/*
 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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/*
 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - 1999 - All Rights Reserved
 *
 * The original version of this source code and documentation
 * is copyrighted and owned by Taligent, Inc., a wholly-owned
 * subsidiary of IBM. These materials are provided under terms
 * of a License Agreement between Taligent and Sun. This technology
 * is protected by multiple US and International patents.
 *
 * This notice and attribution to Taligent may not be removed.
 * Taligent is a registered trademark of Taligent, Inc.
 *
 */

package java.util;

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.jar.JarEntry;
import java.util.spi.ResourceBundleControlProvider;

import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
import sun.util.locale.BaseLocale;
import sun.util.locale.LocaleObjectCache;


/**
 * Resource bundles contain locale-specific objects.  When your program needs a
 * locale-specific resource, a <code>String</code> for example, your program can
 * load it from the resource bundle that is appropriate for the current user's
 * locale. In this way, you can write program code that is largely independent
 * of the user's locale isolating most, if not all, of the locale-specific
 * information in resource bundles.
 *
 * <p>
 * This allows you to write programs that can:
 * <UL>
 * <LI> be easily localized, or translated, into different languages
 * <LI> handle multiple locales at once
 * <LI> be easily modified later to support even more locales
 * </UL>
 *
 * <P>
 * Resource bundles belong to families whose members share a common base
 * name, but whose names also have additional components that identify
 * their locales. For example, the base name of a family of resource
 * bundles might be "MyResources". The family should have a default
 * resource bundle which simply has the same name as its family -
 * "MyResources" - and will be used as the bundle of last resort if a
 * specific locale is not supported. The family can then provide as
 * many locale-specific members as needed, for example a German one
 * named "MyResources_de".
 *
 * <P>
 * Each resource bundle in a family contains the same items, but the items have
 * been translated for the locale represented by that resource bundle.
 * For example, both "MyResources" and "MyResources_de" may have a
 * <code>String</code> that's used on a button for canceling operations.
 * In "MyResources" the <code>String</code> may contain "Cancel" and in
 * "MyResources_de" it may contain "Abbrechen".
 *
 * <P>
 * If there are different resources for different countries, you
 * can make specializations: for example, "MyResources_de_CH" contains objects for
 * the German language (de) in Switzerland (CH). If you want to only
 * modify some of the resources
 * in the specialization, you can do so.
 *
 * <P>
 * When your program needs a locale-specific object, it loads
 * the <code>ResourceBundle</code> class using the
 * {@link #getBundle(java.lang.String, java.util.Locale) getBundle}
 * method:
 * <blockquote>
 * <pre>
 * ResourceBundle myResources =
 *      ResourceBundle.getBundle("MyResources", currentLocale);
 * </pre>
 * </blockquote>
 *
 * <P>
 * Resource bundles contain key/value pairs. The keys uniquely
 * identify a locale-specific object in the bundle. Here's an
 * example of a <code>ListResourceBundle</code> that contains
 * two key/value pairs:
 * <blockquote>
 * <pre>
 * public class MyResources extends ListResourceBundle {
 *     protected Object[][] getContents() {
 *         return new Object[][] {
 *             // LOCALIZE THE SECOND STRING OF EACH ARRAY (e.g., "OK")
 *             {"OkKey", "OK"},
 *             {"CancelKey", "Cancel"},
 *             // END OF MATERIAL TO LOCALIZE
 *        };
 *     }
 * }
 * </pre>
 * </blockquote>
 * Keys are always <code>String</code>s.
 * In this example, the keys are "OkKey" and "CancelKey".
 * In the above example, the values
 * are also <code>String</code>s--"OK" and "Cancel"--but
 * they don't have to be. The values can be any type of object.
 *
 * <P>
 * You retrieve an object from resource bundle using the appropriate
 * getter method. Because "OkKey" and "CancelKey"
 * are both strings, you would use <code>getString</code> to retrieve them:
 * <blockquote>
 * <pre>
 * button1 = new Button(myResources.getString("OkKey"));
 * button2 = new Button(myResources.getString("CancelKey"));
 * </pre>
 * </blockquote>
 * The getter methods all require the key as an argument and return
 * the object if found. If the object is not found, the getter method
 * throws a <code>MissingResourceException</code>.
 *
 * <P>
 * Besides <code>getString</code>, <code>ResourceBundle</code> also provides
 * a method for getting string arrays, <code>getStringArray</code>,
 * as well as a generic <code>getObject</code> method for any other
 * type of object. When using <code>getObject</code>, you'll
 * have to cast the result to the appropriate type. For example:
 * <blockquote>
 * <pre>
 * int[] myIntegers = (int[]) myResources.getObject("intList");
 * </pre>
 * </blockquote>
 *
 * <P>
 * The Java Platform provides two subclasses of <code>ResourceBundle</code>,
 * <code>ListResourceBundle</code> and <code>PropertyResourceBundle</code>,
 * that provide a fairly simple way to create resources.
 * As you saw briefly in a previous example, <code>ListResourceBundle</code>
 * manages its resource as a list of key/value pairs.
 * <code>PropertyResourceBundle</code> uses a properties file to manage
 * its resources.
 *
 * <p>
 * If <code>ListResourceBundle</code> or <code>PropertyResourceBundle</code>
 * do not suit your needs, you can write your own <code>ResourceBundle</code>
 * subclass.  Your subclasses must override two methods: <code>handleGetObject</code>
 * and <code>getKeys()</code>.
 *
 * <p>
 * The implementation of a {@code ResourceBundle} subclass must be thread-safe
 * if it's simultaneously used by multiple threads. The default implementations
 * of the non-abstract methods in this class, and the methods in the direct
 * known concrete subclasses {@code ListResourceBundle} and
 * {@code PropertyResourceBundle} are thread-safe.
 *
 * <h3>ResourceBundle.Control</h3>
 *
 * The {@link ResourceBundle.Control} class provides information necessary
 * to perform the bundle loading process by the <code>getBundle</code>
 * factory methods that take a <code>ResourceBundle.Control</code>
 * instance. You can implement your own subclass in order to enable
 * non-standard resource bundle formats, change the search strategy, or
 * define caching parameters. Refer to the descriptions of the class and the
 * {@link #getBundle(String, Locale, ClassLoader, Control) getBundle}
 * factory method for details.
 *
 * <p><a name="modify_default_behavior">For the {@code getBundle} factory</a>
 * methods that take no {@link Control} instance, their <a
 * href="#default_behavior"> default behavior</a> of resource bundle loading
 * can be modified with <em>installed</em> {@link
 * ResourceBundleControlProvider} implementations. Any installed providers are
 * detected at the {@code ResourceBundle} class loading time. If any of the
 * providers provides a {@link Control} for the given base name, that {@link
 * Control} will be used instead of the default {@link Control}. If there is
 * more than one service provider installed for supporting the same base name,
 * the first one returned from {@link ServiceLoader} will be used.
 *
 * <h3>Cache Management</h3>
 *
 * Resource bundle instances created by the <code>getBundle</code> factory
 * methods are cached by default, and the factory methods return the same
 * resource bundle instance multiple times if it has been
 * cached. <code>getBundle</code> clients may clear the cache, manage the
 * lifetime of cached resource bundle instances using time-to-live values,
 * or specify not to cache resource bundle instances. Refer to the
 * descriptions of the {@linkplain #getBundle(String, Locale, ClassLoader,
 * Control) <code>getBundle</code> factory method}, {@link
 * #clearCache(ClassLoader) clearCache}, {@link
 * Control#getTimeToLive(String, Locale)
 * ResourceBundle.Control.getTimeToLive}, and {@link
 * Control#needsReload(String, Locale, String, ClassLoader, ResourceBundle,
 * long) ResourceBundle.Control.needsReload} for details.
 *
 * <h3>Example</h3>
 *
 * The following is a very simple example of a <code>ResourceBundle</code>
 * subclass, <code>MyResources</code>, that manages two resources (for a larger number of
 * resources you would probably use a <code>Map</code>).
 * Notice that you don't need to supply a value if
 * a "parent-level" <code>ResourceBundle</code> handles the same
 * key with the same value (as for the okKey below).
 * <blockquote>
 * <pre>
 * // default (English language, United States)
 * public class MyResources extends ResourceBundle {
 *     public Object handleGetObject(String key) {
 *         if (key.equals("okKey")) return "Ok";
 *         if (key.equals("cancelKey")) return "Cancel";
 *         return null;
 *     }
 *
 *     public Enumeration&lt;String&gt; getKeys() {
 *         return Collections.enumeration(keySet());
 *     }
 *
 *     // Overrides handleKeySet() so that the getKeys() implementation
 *     // can rely on the keySet() value.
 *     protected Set&lt;String&gt; handleKeySet() {
 *         return new HashSet&lt;String&gt;(Arrays.asList("okKey", "cancelKey"));
 *     }
 * }
 *
 * // German language
 * public class MyResources_de extends MyResources {
 *     public Object handleGetObject(String key) {
 *         // don't need okKey, since parent level handles it.
 *         if (key.equals("cancelKey")) return "Abbrechen";
 *         return null;
 *     }
 *
 *     protected Set&lt;String&gt; handleKeySet() {
 *         return new HashSet&lt;String&gt;(Arrays.asList("cancelKey"));
 *     }
 * }
 * </pre>
 * </blockquote>
 * You do not have to restrict yourself to using a single family of
 * <code>ResourceBundle</code>s. For example, you could have a set of bundles for
 * exception messages, <code>ExceptionResources</code>
 * (<code>ExceptionResources_fr</code>, <code>ExceptionResources_de</code>, ...),
 * and one for widgets, <code>WidgetResource</code> (<code>WidgetResources_fr</code>,
 * <code>WidgetResources_de</code>, ...); breaking up the resources however you like.
 *
 * @see ListResourceBundle
 * @see PropertyResourceBundle
 * @see MissingResourceException
 * @since JDK1.1
 */
public abstract class ResourceBundle {

  /**
   * initial size of the bundle cache
   */
  private static final int INITIAL_CACHE_SIZE = 32;

  /**
   * constant indicating that no resource bundle exists
   */
  private static final ResourceBundle NONEXISTENT_BUNDLE = new ResourceBundle() {
    public Enumeration<String> getKeys() {
      return null;
    }

    protected Object handleGetObject(String key) {
      return null;
    }

    public String toString() {
      return "NONEXISTENT_BUNDLE";
    }
  };


  /**
   * The cache is a map from cache keys (with bundle base name, locale, and
   * class loader) to either a resource bundle or NONEXISTENT_BUNDLE wrapped by a
   * BundleReference.
   *
   * The cache is a ConcurrentMap, allowing the cache to be searched
   * concurrently by multiple threads.  This will also allow the cache keys
   * to be reclaimed along with the ClassLoaders they reference.
   *
   * This variable would be better named "cache", but we keep the old
   * name for compatibility with some workarounds for bug 4212439.
   */
  private static final ConcurrentMap<CacheKey, BundleReference> cacheList
      = new ConcurrentHashMap<>(INITIAL_CACHE_SIZE);

  /**
   * Queue for reference objects referring to class loaders or bundles.
   */
  private static final ReferenceQueue<Object> referenceQueue = new ReferenceQueue<>();

  /**
   * Returns the base name of this bundle, if known, or {@code null} if unknown.
   *
   * If not null, then this is the value of the {@code baseName} parameter
   * that was passed to the {@code ResourceBundle.getBundle(...)} method
   * when the resource bundle was loaded.
   *
   * @return The base name of the resource bundle, as provided to and expected by the {@code
   * ResourceBundle.getBundle(...)} methods.
   * @see #getBundle(java.lang.String, java.util.Locale, java.lang.ClassLoader)
   * @since 1.8
   */
  public String getBaseBundleName() {
    return name;
  }

  /**
   * The parent bundle of this bundle.
   * The parent bundle is searched by {@link #getObject getObject}
   * when this bundle does not contain a particular resource.
   */
  protected ResourceBundle parent = null;

  /**
   * The locale for this bundle.
   */
  private Locale locale = null;

  /**
   * The base bundle name for this bundle.
   */
  private String name;

  /**
   * The flag indicating this bundle has expired in the cache.
   */
  private volatile boolean expired;

  /**
   * The back link to the cache key. null if this bundle isn't in
   * the cache (yet) or has expired.
   */
  private volatile CacheKey cacheKey;

  /**
   * A Set of the keys contained only in this ResourceBundle.
   */
  private volatile Set<String> keySet;

  private static final List<ResourceBundleControlProvider> providers;

  static {
    List<ResourceBundleControlProvider> list = null;
    ServiceLoader<ResourceBundleControlProvider> serviceLoaders
        = ServiceLoader.loadInstalled(ResourceBundleControlProvider.class);
    for (ResourceBundleControlProvider provider : serviceLoaders) {
      if (list == null) {
        list = new ArrayList<>();
      }
      list.add(provider);
    }
    providers = list;
  }

  /**
   * Sole constructor.  (For invocation by subclass constructors, typically
   * implicit.)
   */
  public ResourceBundle() {
  }

  /**
   * Gets a string for the given key from this resource bundle or one of its parents.
   * Calling this method is equivalent to calling
   * <blockquote>
   * <code>(String) {@link #getObject(java.lang.String) getObject}(key)</code>.
   * </blockquote>
   *
   * @param key the key for the desired string
   * @return the string for the given key
   * @throws NullPointerException if <code>key</code> is <code>null</code>
   * @throws MissingResourceException if no object for the given key can be found
   * @throws ClassCastException if the object found for the given key is not a string
   */
  public final String getString(String key) {
    return (String) getObject(key);
  }

  /**
   * Gets a string array for the given key from this resource bundle or one of its parents.
   * Calling this method is equivalent to calling
   * <blockquote>
   * <code>(String[]) {@link #getObject(java.lang.String) getObject}(key)</code>.
   * </blockquote>
   *
   * @param key the key for the desired string array
   * @return the string array for the given key
   * @throws NullPointerException if <code>key</code> is <code>null</code>
   * @throws MissingResourceException if no object for the given key can be found
   * @throws ClassCastException if the object found for the given key is not a string array
   */
  public final String[] getStringArray(String key) {
    return (String[]) getObject(key);
  }

  /**
   * Gets an object for the given key from this resource bundle or one of its parents.
   * This method first tries to obtain the object from this resource bundle using
   * {@link #handleGetObject(java.lang.String) handleGetObject}.
   * If not successful, and the parent resource bundle is not null,
   * it calls the parent's <code>getObject</code> method.
   * If still not successful, it throws a MissingResourceException.
   *
   * @param key the key for the desired object
   * @return the object for the given key
   * @throws NullPointerException if <code>key</code> is <code>null</code>
   * @throws MissingResourceException if no object for the given key can be found
   */
  public final Object getObject(String key) {
    Object obj = handleGetObject(key);
    if (obj == null) {
      if (parent != null) {
        obj = parent.getObject(key);
      }
      if (obj == null) {
        throw new MissingResourceException("Can't find resource for bundle "
            + this.getClass().getName()
            + ", key " + key,
            this.getClass().getName(),
            key);
      }
    }
    return obj;
  }

  /**
   * Returns the locale of this resource bundle. This method can be used after a
   * call to getBundle() to determine whether the resource bundle returned really
   * corresponds to the requested locale or is a fallback.
   *
   * @return the locale of this resource bundle
   */
  public Locale getLocale() {
    return locale;
  }

  /*
   * Automatic determination of the ClassLoader to be used to load
   * resources on behalf of the client.
   */
  private static ClassLoader getLoader(Class<?> caller) {
    ClassLoader cl = caller == null ? null : caller.getClassLoader();
    if (cl == null) {
      // When the caller's loader is the boot class loader, cl is null
      // here. In that case, ClassLoader.getSystemClassLoader() may
      // return the same class loader that the application is
      // using. We therefore use a wrapper ClassLoader to create a
      // separate scope for bundles loaded on behalf of the Java
      // runtime so that these bundles cannot be returned from the
      // cache to the application (5048280).
      cl = RBClassLoader.INSTANCE;
    }
    return cl;
  }

  /**
   * A wrapper of ClassLoader.getSystemClassLoader().
   */
  private static class RBClassLoader extends ClassLoader {

    private static final RBClassLoader INSTANCE = AccessController.doPrivileged(
        new PrivilegedAction<RBClassLoader>() {
          public RBClassLoader run() {
            return new RBClassLoader();
          }
        });
    private static final ClassLoader loader = ClassLoader.getSystemClassLoader();

    private RBClassLoader() {
    }

    public Class<?> loadClass(String name) throws ClassNotFoundException {
      if (loader != null) {
        return loader.loadClass(name);
      }
      return Class.forName(name);
    }

    public URL getResource(String name) {
      if (loader != null) {
        return loader.getResource(name);
      }
      return ClassLoader.getSystemResource(name);
    }

    public InputStream getResourceAsStream(String name) {
      if (loader != null) {
        return loader.getResourceAsStream(name);
      }
      return ClassLoader.getSystemResourceAsStream(name);
    }
  }

  /**
   * Sets the parent bundle of this bundle.
   * The parent bundle is searched by {@link #getObject getObject}
   * when this bundle does not contain a particular resource.
   *
   * @param parent this bundle's parent bundle.
   */
  protected void setParent(ResourceBundle parent) {
    assert parent != NONEXISTENT_BUNDLE;
    this.parent = parent;
  }

  /**
   * Key used for cached resource bundles.  The key checks the base
   * name, the locale, and the class loader to determine if the
   * resource is a match to the requested one. The loader may be
   * null, but the base name and the locale must have a non-null
   * value.
   */
  private static class CacheKey implements Cloneable {

    // These three are the actual keys for lookup in Map.
    private String name;
    private Locale locale;
    private LoaderReference loaderRef;

    // bundle format which is necessary for calling
    // Control.needsReload().
    private String format;

    // These time values are in CacheKey so that NONEXISTENT_BUNDLE
    // doesn't need to be cloned for caching.

    // The time when the bundle has been loaded
    private volatile long loadTime;

    // The time when the bundle expires in the cache, or either
    // Control.TTL_DONT_CACHE or Control.TTL_NO_EXPIRATION_CONTROL.
    private volatile long expirationTime;

    // Placeholder for an error report by a Throwable
    private Throwable cause;

    // Hash code value cache to avoid recalculating the hash code
    // of this instance.
    private int hashCodeCache;

    CacheKey(String baseName, Locale locale, ClassLoader loader) {
      this.name = baseName;
      this.locale = locale;
      if (loader == null) {
        this.loaderRef = null;
      } else {
        loaderRef = new LoaderReference(loader, referenceQueue, this);
      }
      calculateHashCode();
    }

    String getName() {
      return name;
    }

    CacheKey setName(String baseName) {
      if (!this.name.equals(baseName)) {
        this.name = baseName;
        calculateHashCode();
      }
      return this;
    }

    Locale getLocale() {
      return locale;
    }

    CacheKey setLocale(Locale locale) {
      if (!this.locale.equals(locale)) {
        this.locale = locale;
        calculateHashCode();
      }
      return this;
    }

    ClassLoader getLoader() {
      return (loaderRef != null) ? loaderRef.get() : null;
    }

    public boolean equals(Object other) {
      if (this == other) {
        return true;
      }
      try {
        final CacheKey otherEntry = (CacheKey) other;
        //quick check to see if they are not equal
        if (hashCodeCache != otherEntry.hashCodeCache) {
          return false;
        }
        //are the names the same?
        if (!name.equals(otherEntry.name)) {
          return false;
        }
        // are the locales the same?
        if (!locale.equals(otherEntry.locale)) {
          return false;
        }
        //are refs (both non-null) or (both null)?
        if (loaderRef == null) {
          return otherEntry.loaderRef == null;
        }
        ClassLoader loader = loaderRef.get();
        return (otherEntry.loaderRef != null)
            // with a null reference we can no longer find
            // out which class loader was referenced; so
            // treat it as unequal
            && (loader != null)
            && (loader == otherEntry.loaderRef.get());
      } catch (NullPointerException | ClassCastException e) {
      }
      return false;
    }

    public int hashCode() {
      return hashCodeCache;
    }

    private void calculateHashCode() {
      hashCodeCache = name.hashCode() << 3;
      hashCodeCache ^= locale.hashCode();
      ClassLoader loader = getLoader();
      if (loader != null) {
        hashCodeCache ^= loader.hashCode();
      }
    }

    public Object clone() {
      try {
        CacheKey clone = (CacheKey) super.clone();
        if (loaderRef != null) {
          clone.loaderRef = new LoaderReference(loaderRef.get(),
              referenceQueue, clone);
        }
        // Clear the reference to a Throwable
        clone.cause = null;
        return clone;
      } catch (CloneNotSupportedException e) {
        //this should never happen
        throw new InternalError(e);
      }
    }

    String getFormat() {
      return format;
    }

    void setFormat(String format) {
      this.format = format;
    }

    private void setCause(Throwable cause) {
      if (this.cause == null) {
        this.cause = cause;
      } else {
        // Override the cause if the previous one is
        // ClassNotFoundException.
        if (this.cause instanceof ClassNotFoundException) {
          this.cause = cause;
        }
      }
    }

    private Throwable getCause() {
      return cause;
    }

    public String toString() {
      String l = locale.toString();
      if (l.length() == 0) {
        if (locale.getVariant().length() != 0) {
          l = "__" + locale.getVariant();
        } else {
          l = "\"\"";
        }
      }
      return "CacheKey[" + name + ", lc=" + l + ", ldr=" + getLoader()
          + "(format=" + format + ")]";
    }
  }

  /**
   * The common interface to get a CacheKey in LoaderReference and
   * BundleReference.
   */
  private static interface CacheKeyReference {

    public CacheKey getCacheKey();
  }

  /**
   * References to class loaders are weak references, so that they can be
   * garbage collected when nobody else is using them. The ResourceBundle
   * class has no reason to keep class loaders alive.
   */
  private static class LoaderReference extends WeakReference<ClassLoader>
      implements CacheKeyReference {

    private CacheKey cacheKey;

    LoaderReference(ClassLoader referent, ReferenceQueue<Object> q, CacheKey key) {
      super(referent, q);
      cacheKey = key;
    }

    public CacheKey getCacheKey() {
      return cacheKey;
    }
  }

  /**
   * References to bundles are soft references so that they can be garbage
   * collected when they have no hard references.
   */
  private static class BundleReference extends SoftReference<ResourceBundle>
      implements CacheKeyReference {

    private CacheKey cacheKey;

    BundleReference(ResourceBundle referent, ReferenceQueue<Object> q, CacheKey key) {
      super(referent, q);
      cacheKey = key;
    }

    public CacheKey getCacheKey() {
      return cacheKey;
    }
  }

  /**
   * Gets a resource bundle using the specified base name, the default locale,
   * and the caller's class loader. Calling this method is equivalent to calling
   * <blockquote>
   * <code>getBundle(baseName, Locale.getDefault(), this.getClass().getClassLoader())</code>,
   * </blockquote>
   * except that <code>getClassLoader()</code> is run with the security
   * privileges of <code>ResourceBundle</code>.
   * See {@link #getBundle(String, Locale, ClassLoader) getBundle}
   * for a complete description of the search and instantiation strategy.
   *
   * @param baseName the base name of the resource bundle, a fully qualified class name
   * @return a resource bundle for the given base name and the default locale
   * @throws java.lang.NullPointerException if <code>baseName</code> is <code>null</code>
   * @throws MissingResourceException if no resource bundle for the specified base name can be
   * found
   */
  @CallerSensitive
  public static final ResourceBundle getBundle(String baseName) {
    return getBundleImpl(baseName, Locale.getDefault(),
        getLoader(Reflection.getCallerClass()),
        getDefaultControl(baseName));
  }

  /**
   * Returns a resource bundle using the specified base name, the
   * default locale and the specified control. Calling this method
   * is equivalent to calling
   * <pre>
   * getBundle(baseName, Locale.getDefault(),
   *           this.getClass().getClassLoader(), control),
   * </pre>
   * except that <code>getClassLoader()</code> is run with the security
   * privileges of <code>ResourceBundle</code>.  See {@link
   * #getBundle(String, Locale, ClassLoader, Control) getBundle} for the
   * complete description of the resource bundle loading process with a
   * <code>ResourceBundle.Control</code>.
   *
   * @param baseName the base name of the resource bundle, a fully qualified class name
   * @param control the control which gives information for the resource bundle loading process
   * @return a resource bundle for the given base name and the default locale
   * @throws NullPointerException if <code>baseName</code> or <code>control</code> is
   * <code>null</code>
   * @throws MissingResourceException if no resource bundle for the specified base name can be
   * found
   * @throws IllegalArgumentException if the given <code>control</code> doesn't perform properly
   * (e.g., <code>control.getCandidateLocales</code> returns null.) Note that validation of
   * <code>control</code> is performed as needed.
   * @since 1.6
   */
  @CallerSensitive
  public static final ResourceBundle getBundle(String baseName,
      Control control) {
    return getBundleImpl(baseName, Locale.getDefault(),
        getLoader(Reflection.getCallerClass()),
        control);
  }

  /**
   * Gets a resource bundle using the specified base name and locale,
   * and the caller's class loader. Calling this method is equivalent to calling
   * <blockquote>
   * <code>getBundle(baseName, locale, this.getClass().getClassLoader())</code>,
   * </blockquote>
   * except that <code>getClassLoader()</code> is run with the security
   * privileges of <code>ResourceBundle</code>.
   * See {@link #getBundle(String, Locale, ClassLoader) getBundle}
   * for a complete description of the search and instantiation strategy.
   *
   * @param baseName the base name of the resource bundle, a fully qualified class name
   * @param locale the locale for which a resource bundle is desired
   * @return a resource bundle for the given base name and locale
   * @throws NullPointerException if <code>baseName</code> or <code>locale</code> is
   * <code>null</code>
   * @throws MissingResourceException if no resource bundle for the specified base name can be
   * found
   */
  @CallerSensitive
  public static final ResourceBundle getBundle(String baseName,
      Locale locale) {
    return getBundleImpl(baseName, locale,
        getLoader(Reflection.getCallerClass()),
        getDefaultControl(baseName));
  }

  /**
   * Returns a resource bundle using the specified base name, target
   * locale and control, and the caller's class loader. Calling this
   * method is equivalent to calling
   * <pre>
   * getBundle(baseName, targetLocale, this.getClass().getClassLoader(),
   *           control),
   * </pre>
   * except that <code>getClassLoader()</code> is run with the security
   * privileges of <code>ResourceBundle</code>.  See {@link
   * #getBundle(String, Locale, ClassLoader, Control) getBundle} for the
   * complete description of the resource bundle loading process with a
   * <code>ResourceBundle.Control</code>.
   *
   * @param baseName the base name of the resource bundle, a fully qualified class name
   * @param targetLocale the locale for which a resource bundle is desired
   * @param control the control which gives information for the resource bundle loading process
   * @return a resource bundle for the given base name and a <code>Locale</code> in
   * <code>locales</code>
   * @throws NullPointerException if <code>baseName</code>, <code>locales</code> or
   * <code>control</code> is <code>null</code>
   * @throws MissingResourceException if no resource bundle for the specified base name in any of
   * the <code>locales</code> can be found.
   * @throws IllegalArgumentException if the given <code>control</code> doesn't perform properly
   * (e.g., <code>control.getCandidateLocales</code> returns null.) Note that validation of
   * <code>control</code> is performed as needed.
   * @since 1.6
   */
  @CallerSensitive
  public static final ResourceBundle getBundle(String baseName, Locale targetLocale,
      Control control) {
    return getBundleImpl(baseName, targetLocale,
        getLoader(Reflection.getCallerClass()),
        control);
  }

  /**
   * Gets a resource bundle using the specified base name, locale, and class loader.
   *
   * <p>This method behaves the same as calling {@link #getBundle(String, Locale, ClassLoader,
   * Control)} passing a default instance of {@link Control} unless another {@link Control} is
   * provided with the {@link ResourceBundleControlProvider} SPI. Refer to the description of <a
   * href="#modify_default_behavior">modifying the default behavior</a>.
   *
   * <p><a name="default_behavior">The following describes the default behavior</a>.
   *
   * <p><code>getBundle</code> uses the base name, the specified locale, and the default locale
   * (obtained from {@link java.util.Locale#getDefault() Locale.getDefault}) to generate a sequence
   * of <a name="candidates"><em>candidate bundle names</em></a>.  If the specified locale's
   * language, script, country, and variant are all empty strings, then the base name is the only
   * candidate bundle name.  Otherwise, a list of candidate locales is generated from the attribute
   * values of the specified locale (language, script, country and variant) and appended to the base
   * name.  Typically, this will look like the following:
   *
   * <pre>
   *     baseName + "_" + language + "_" + script + "_" + country + "_" + variant
   *     baseName + "_" + language + "_" + script + "_" + country
   *     baseName + "_" + language + "_" + script
   *     baseName + "_" + language + "_" + country + "_" + variant
   *     baseName + "_" + language + "_" + country
   *     baseName + "_" + language
   * </pre>
   *
   * <p>Candidate bundle names where the final component is an empty string are omitted, along with
   * the underscore.  For example, if country is an empty string, the second and the fifth candidate
   * bundle names above would be omitted.  Also, if script is an empty string, the candidate names
   * including script are omitted.  For example, a locale with language "de" and variant "JAVA" will
   * produce candidate names with base name "MyResource" below.
   *
   * <pre>
   *     MyResource_de__JAVA
   *     MyResource_de
   * </pre>
   *
   * In the case that the variant contains one or more underscores ('_'), a sequence of bundle names
   * generated by truncating the last underscore and the part following it is inserted after a
   * candidate bundle name with the original variant.  For example, for a locale with language "en",
   * script "Latn, country "US" and variant "WINDOWS_VISTA", and bundle base name "MyResource", the
   * list of candidate bundle names below is generated:
   *
   * <pre>
   * MyResource_en_Latn_US_WINDOWS_VISTA
   * MyResource_en_Latn_US_WINDOWS
   * MyResource_en_Latn_US
   * MyResource_en_Latn
   * MyResource_en_US_WINDOWS_VISTA
   * MyResource_en_US_WINDOWS
   * MyResource_en_US
   * MyResource_en
   * </pre>
   *
   * <blockquote><b>Note:</b> For some <code>Locale</code>s, the list of candidate bundle names
   * contains extra names, or the order of bundle names is slightly modified.  See the description
   * of the default implementation of {@link Control#getCandidateLocales(String, Locale)
   * getCandidateLocales} for details.</blockquote>
   *
   * <p><code>getBundle</code> then iterates over the candidate bundle names to find the first one
   * for which it can <em>instantiate</em> an actual resource bundle. It uses the default controls'
   * {@link Control#getFormats getFormats} method, which generates two bundle names for each
   * generated name, the first a class name and the second a properties file name. For each
   * candidate bundle name, it attempts to create a resource bundle:
   *
   * <ul><li>First, it attempts to load a class using the generated class name. If such a class can
   * be found and loaded using the specified class loader, is assignment compatible with
   * ResourceBundle, is accessible from ResourceBundle, and can be instantiated,
   * <code>getBundle</code> creates a new instance of this class and uses it as the <em>result
   * resource bundle</em>.
   *
   * <li>Otherwise, <code>getBundle</code> attempts to locate a property resource file using the
   * generated properties file name.  It generates a path name from the candidate bundle name by
   * replacing all "." characters with "/" and appending the string ".properties".  It attempts to
   * find a "resource" with this name using {@link java.lang.ClassLoader#getResource(java.lang.String)
   * ClassLoader.getResource}.  (Note that a "resource" in the sense of <code>getResource</code> has
   * nothing to do with the contents of a resource bundle, it is just a container of data, such as a
   * file.)  If it finds a "resource", it attempts to create a new {@link PropertyResourceBundle}
   * instance from its contents.  If successful, this instance becomes the <em>result resource
   * bundle</em>.  </ul>
   *
   * <p>This continues until a result resource bundle is instantiated or the list of candidate
   * bundle names is exhausted.  If no matching resource bundle is found, the default control's
   * {@link Control#getFallbackLocale getFallbackLocale} method is called, which returns the current
   * default locale.  A new sequence of candidate locale names is generated using this locale and
   * and searched again, as above.
   *
   * <p>If still no result bundle is found, the base name alone is looked up. If this still fails, a
   * <code>MissingResourceException</code> is thrown.
   *
   * <p><a name="parent_chain"> Once a result resource bundle has been found, its <em>parent
   * chain</em> is instantiated</a>.  If the result bundle already has a parent (perhaps because it
   * was returned from a cache) the chain is complete.
   *
   * <p>Otherwise, <code>getBundle</code> examines the remainder of the candidate locale list that
   * was used during the pass that generated the result resource bundle.  (As before, candidate
   * bundle names where the final component is an empty string are omitted.)  When it comes to the
   * end of the candidate list, it tries the plain bundle name.  With each of the candidate bundle
   * names it attempts to instantiate a resource bundle (first looking for a class and then a
   * properties file, as described above).
   *
   * <p>Whenever it succeeds, it calls the previously instantiated resource bundle's {@link
   * #setParent(java.util.ResourceBundle) setParent} method with the new resource bundle.  This
   * continues until the list of names is exhausted or the current bundle already has a non-null
   * parent.
   *
   * <p>Once the parent chain is complete, the bundle is returned.
   *
   * <p><b>Note:</b> <code>getBundle</code> caches instantiated resource bundles and might return
   * the same resource bundle instance multiple times.
   *
   * <p><b>Note:</b>The <code>baseName</code> argument should be a fully qualified class name.
   * However, for compatibility with earlier versions, Sun's Java SE Runtime Environments do not
   * verify this, and so it is possible to access <code>PropertyResourceBundle</code>s by specifying
   * a path name (using "/") instead of a fully qualified class name (using ".").
   *
   * <p><a name="default_behavior_example"> <strong>Example:</strong></a> <p> The following class
   * and property files are provided:
   * <pre>
   *     MyResources.class
   *     MyResources.properties
   *     MyResources_fr.properties
   *     MyResources_fr_CH.class
   *     MyResources_fr_CH.properties
   *     MyResources_en.properties
   *     MyResources_es_ES.class
   * </pre>
   *
   * The contents of all files are valid (that is, public non-abstract subclasses of
   * <code>ResourceBundle</code> for the ".class" files, syntactically correct ".properties" files).
   * The default locale is <code>Locale("en", "GB")</code>.
   *
   * <p>Calling <code>getBundle</code> with the locale arguments below will instantiate resource
   * bundles as follows:
   *
   * <table summary="getBundle() locale to resource bundle mapping"> <tr><td>Locale("fr",
   * "CH")</td><td>MyResources_fr_CH.class, parent MyResources_fr.properties, parent
   * MyResources.class</td></tr> <tr><td>Locale("fr", "FR")</td><td>MyResources_fr.properties,
   * parent MyResources.class</td></tr> <tr><td>Locale("de", "DE")</td><td>MyResources_en.properties,
   * parent MyResources.class</td></tr> <tr><td>Locale("en", "US")</td><td>MyResources_en.properties,
   * parent MyResources.class</td></tr> <tr><td>Locale("es", "ES")</td><td>MyResources_es_ES.class,
   * parent MyResources.class</td></tr> </table>
   *
   * <p>The file MyResources_fr_CH.properties is never used because it is hidden by the
   * MyResources_fr_CH.class. Likewise, MyResources.properties is also hidden by MyResources.class.
   *
   * @param baseName the base name of the resource bundle, a fully qualified class name
   * @param locale the locale for which a resource bundle is desired
   * @param loader the class loader from which to load the resource bundle
   * @return a resource bundle for the given base name and locale
   * @throws java.lang.NullPointerException if <code>baseName</code>, <code>locale</code>, or
   * <code>loader</code> is <code>null</code>
   * @throws MissingResourceException if no resource bundle for the specified base name can be
   * found
   * @since 1.2
   */
  public static ResourceBundle getBundle(String baseName, Locale locale,
      ClassLoader loader) {
    if (loader == null) {
      throw new NullPointerException();
    }
    return getBundleImpl(baseName, locale, loader, getDefaultControl(baseName));
  }

  /**
   * Returns a resource bundle using the specified base name, target locale, class loader and
   * control. Unlike the {@linkplain #getBundle(String, Locale, ClassLoader) <code>getBundle</code>
   * factory methods with no <code>control</code> argument}, the given <code>control</code>
   * specifies how to locate and instantiate resource bundles. Conceptually, the bundle loading
   * process with the given <code>control</code> is performed in the following steps.
   *
   * <ol> <li>This factory method looks up the resource bundle in the cache for the specified
   * <code>baseName</code>, <code>targetLocale</code> and <code>loader</code>.  If the requested
   * resource bundle instance is found in the cache and the time-to-live periods of the instance and
   * all of its parent instances have not expired, the instance is returned to the caller.
   * Otherwise, this factory method proceeds with the loading process below.</li>
   *
   * <li>The {@link ResourceBundle.Control#getFormats(String) control.getFormats} method is called
   * to get resource bundle formats to produce bundle or resource names. The strings
   * <code>"java.class"</code> and <code>"java.properties"</code> designate class-based and
   * {@linkplain PropertyResourceBundle property}-based resource bundles, respectively. Other
   * strings starting with <code>"java."</code> are reserved for future extensions and must not be
   * used for application-defined formats. Other strings designate application-defined
   * formats.</li>
   *
   * <li>The {@link ResourceBundle.Control#getCandidateLocales(String, Locale)
   * control.getCandidateLocales} method is called with the target locale to get a list of
   * <em>candidate <code>Locale</code>s</em> for which resource bundles are searched.</li>
   *
   * <li>The {@link ResourceBundle.Control#newBundle(String, Locale, String, ClassLoader, boolean)
   * control.newBundle} method is called to instantiate a <code>ResourceBundle</code> for the base
   * bundle name, a candidate locale, and a format. (Refer to the note on the cache lookup below.)
   * This step is iterated over all combinations of the candidate locales and formats until the
   * <code>newBundle</code> method returns a <code>ResourceBundle</code> instance or the iteration
   * has used up all the combinations. For example, if the candidate locales are <code>Locale("de",
   * "DE")</code>, <code>Locale("de")</code> and <code>Locale("")</code> and the formats are
   * <code>"java.class"</code> and <code>"java.properties"</code>, then the following is the
   * sequence of locale-format combinations to be used to call <code>control.newBundle</code>.
   *
   * <table style="width: 50%; text-align: left; margin-left: 40px;" border="0" cellpadding="2"
   * cellspacing="2" summary="locale-format combinations for newBundle"> <tbody> <tr> <td
   * style="vertical-align: top; text-align: left; font-weight: bold; width:
   * 50%;"><code>Locale</code><br> </td> <td style="vertical-align: top; text-align: left;
   * font-weight: bold; width: 50%;"><code>format</code><br> </td> </tr> <tr> <td
   * style="vertical-align: top; width: 50%;"><code>Locale("de", "DE")</code><br> </td> <td
   * style="vertical-align: top; width: 50%;"><code>java.class</code><br> </td> </tr> <tr> <td
   * style="vertical-align: top; width: 50%;"><code>Locale("de", "DE")</code></td> <td
   * style="vertical-align: top; width: 50%;"><code>java.properties</code><br> </td> </tr> <tr> <td
   * style="vertical-align: top; width: 50%;"><code>Locale("de")</code></td> <td
   * style="vertical-align: top; width: 50%;"><code>java.class</code></td> </tr> <tr> <td
   * style="vertical-align: top; width: 50%;"><code>Locale("de")</code></td> <td
   * style="vertical-align: top; width: 50%;"><code>java.properties</code></td> </tr> <tr> <td
   * style="vertical-align: top; width: 50%;"><code>Locale("")</code><br> </td> <td
   * style="vertical-align: top; width: 50%;"><code>java.class</code></td> </tr> <tr> <td
   * style="vertical-align: top; width: 50%;"><code>Locale("")</code></td> <td
   * style="vertical-align: top; width: 50%;"><code>java.properties</code></td> </tr> </tbody>
   * </table> </li>
   *
   * <li>If the previous step has found no resource bundle, proceed to Step 6. If a bundle has been
   * found that is a base bundle (a bundle for <code>Locale("")</code>), and the candidate locale
   * list only contained <code>Locale("")</code>, return the bundle to the caller. If a bundle has
   * been found that is a base bundle, but the candidate locale list contained locales other than
   * Locale(""), put the bundle on hold and proceed to Step 6. If a bundle has been found that is
   * not a base bundle, proceed to Step 7.</li>
   *
   * <li>The {@link ResourceBundle.Control#getFallbackLocale(String, Locale)
   * control.getFallbackLocale} method is called to get a fallback locale (alternative to the
   * current target locale) to try further finding a resource bundle. If the method returns a
   * non-null locale, it becomes the next target locale and the loading process starts over from
   * Step 3. Otherwise, if a base bundle was found and put on hold in a previous Step 5, it is
   * returned to the caller now. Otherwise, a MissingResourceException is thrown.</li>
   *
   * <li>At this point, we have found a resource bundle that's not the base bundle. If this bundle
   * set its parent during its instantiation, it is returned to the caller. Otherwise, its <a
   * href="./ResourceBundle.html#parent_chain">parent chain</a> is instantiated based on the list of
   * candidate locales from which it was found. Finally, the bundle is returned to the caller.</li>
   * </ol>
   *
   * <p>During the resource bundle loading process above, this factory method looks up the cache
   * before calling the {@link Control#newBundle(String, Locale, String, ClassLoader, boolean)
   * control.newBundle} method.  If the time-to-live period of the resource bundle found in the
   * cache has expired, the factory method calls the {@link ResourceBundle.Control#needsReload(String,
   * Locale, String, ClassLoader, ResourceBundle, long) control.needsReload} method to determine
   * whether the resource bundle needs to be reloaded. If reloading is required, the factory method
   * calls <code>control.newBundle</code> to reload the resource bundle.  If
   * <code>control.newBundle</code> returns <code>null</code>, the factory method puts a dummy
   * resource bundle in the cache as a mark of nonexistent resource bundles in order to avoid lookup
   * overhead for subsequent requests. Such dummy resource bundles are under the same expiration
   * control as specified by <code>control</code>.
   *
   * <p>All resource bundles loaded are cached by default. Refer to {@link
   * Control#getTimeToLive(String, Locale) control.getTimeToLive} for details.
   *
   * <p>The following is an example of the bundle loading process with the default
   * <code>ResourceBundle.Control</code> implementation.
   *
   * <p>Conditions: <ul> <li>Base bundle name: <code>foo.bar.Messages</code> <li>Requested
   * <code>Locale</code>: {@link Locale#ITALY}</li> <li>Default <code>Locale</code>: {@link
   * Locale#FRENCH}</li> <li>Available resource bundles: <code>foo/bar/Messages_fr.properties</code>
   * and <code>foo/bar/Messages.properties</code></li> </ul>
   *
   * <p>First, <code>getBundle</code> tries loading a resource bundle in the following sequence.
   *
   * <ul> <li>class <code>foo.bar.Messages_it_IT</code> <li>file <code>foo/bar/Messages_it_IT.properties</code>
   * <li>class <code>foo.bar.Messages_it</code></li> <li>file <code>foo/bar/Messages_it.properties</code></li>
   * <li>class <code>foo.bar.Messages</code></li> <li>file <code>foo/bar/Messages.properties</code></li>
   * </ul>
   *
   * <p>At this point, <code>getBundle</code> finds <code>foo/bar/Messages.properties</code>, which
   * is put on hold because it's the base bundle.  <code>getBundle</code> calls {@link
   * Control#getFallbackLocale(String, Locale) control.getFallbackLocale("foo.bar.Messages",
   * Locale.ITALY)} which returns <code>Locale.FRENCH</code>. Next, <code>getBundle</code> tries
   * loading a bundle in the following sequence.
   *
   * <ul> <li>class <code>foo.bar.Messages_fr</code></li> <li>file <code>foo/bar/Messages_fr.properties</code></li>
   * <li>class <code>foo.bar.Messages</code></li> <li>file <code>foo/bar/Messages.properties</code></li>
   * </ul>
   *
   * <p><code>getBundle</code> finds <code>foo/bar/Messages_fr.properties</code> and creates a
   * <code>ResourceBundle</code> instance. Then, <code>getBundle</code> sets up its parent chain
   * from the list of the candidate locales.  Only <code>foo/bar/Messages.properties</code> is found
   * in the list and <code>getBundle</code> creates a <code>ResourceBundle</code> instance that
   * becomes the parent of the instance for <code>foo/bar/Messages_fr.properties</code>.
   *
   * @param baseName the base name of the resource bundle, a fully qualified class name
   * @param targetLocale the locale for which a resource bundle is desired
   * @param loader the class loader from which to load the resource bundle
   * @param control the control which gives information for the resource bundle loading process
   * @return a resource bundle for the given base name and locale
   * @throws NullPointerException if <code>baseName</code>, <code>targetLocale</code>,
   * <code>loader</code>, or <code>control</code> is <code>null</code>
   * @throws MissingResourceException if no resource bundle for the specified base name can be
   * found
   * @throws IllegalArgumentException if the given <code>control</code> doesn't perform properly
   * (e.g., <code>control.getCandidateLocales</code> returns null.) Note that validation of
   * <code>control</code> is performed as needed.
   * @since 1.6
   */
  public static ResourceBundle getBundle(String baseName, Locale targetLocale,
      ClassLoader loader, Control control) {
    if (loader == null || control == null) {
      throw new NullPointerException();
    }
    return getBundleImpl(baseName, targetLocale, loader, control);
  }

  private static Control getDefaultControl(String baseName) {
    if (providers != null) {
      for (ResourceBundleControlProvider provider : providers) {
        Control control = provider.getControl(baseName);
        if (control != null) {
          return control;
        }
      }
    }
    return Control.INSTANCE;
  }

  private static ResourceBundle getBundleImpl(String baseName, Locale locale,
      ClassLoader loader, Control control) {
    if (locale == null || control == null) {
      throw new NullPointerException();
    }

    // We create a CacheKey here for use by this call. The base
    // name and loader will never change during the bundle loading
    // process. We have to make sure that the locale is set before
    // using it as a cache key.
    CacheKey cacheKey = new CacheKey(baseName, locale, loader);
    ResourceBundle bundle = null;

    // Quick lookup of the cache.
    BundleReference bundleRef = cacheList.get(cacheKey);
    if (bundleRef != null) {
      bundle = bundleRef.get();
      bundleRef = null;
    }

    // If this bundle and all of its parents are valid (not expired),
    // then return this bundle. If any of the bundles is expired, we
    // don't call control.needsReload here but instead drop into the
    // complete loading process below.
    if (isValidBundle(bundle) && hasValidParentChain(bundle)) {
      return bundle;
    }

    // No valid bundle was found in the cache, so we need to load the
    // resource bundle and its parents.

    boolean isKnownControl = (control == Control.INSTANCE) ||
        (control instanceof SingleFormatControl);
    List<String> formats = control.getFormats(baseName);
    if (!isKnownControl && !checkList(formats)) {
      throw new IllegalArgumentException("Invalid Control: getFormats");
    }

    ResourceBundle baseBundle = null;
    for (Locale targetLocale = locale;
        targetLocale != null;
        targetLocale = control.getFallbackLocale(baseName, targetLocale)) {
      List<Locale> candidateLocales = control.getCandidateLocales(baseName, targetLocale);
      if (!isKnownControl && !checkList(candidateLocales)) {
        throw new IllegalArgumentException("Invalid Control: getCandidateLocales");
      }

      bundle = findBundle(cacheKey, candidateLocales, formats, 0, control, baseBundle);

      // If the loaded bundle is the base bundle and exactly for the
      // requested locale or the only candidate locale, then take the
      // bundle as the resulting one. If the loaded bundle is the base
      // bundle, it's put on hold until we finish processing all
      // fallback locales.
      if (isValidBundle(bundle)) {
        boolean isBaseBundle = Locale.ROOT.equals(bundle.locale);
        if (!isBaseBundle || bundle.locale.equals(locale)
            || (candidateLocales.size() == 1
            && bundle.locale.equals(candidateLocales.get(0)))) {
          break;
        }

        // If the base bundle has been loaded, keep the reference in
        // baseBundle so that we can avoid any redundant loading in case
        // the control specify not to cache bundles.
        if (isBaseBundle && baseBundle == null) {
          baseBundle = bundle;
        }
      }
    }

    if (bundle == null) {
      if (baseBundle == null) {
        throwMissingResourceException(baseName, locale, cacheKey.getCause());
      }
      bundle = baseBundle;
    }

    return bundle;
  }

  /**
   * Checks if the given <code>List</code> is not null, not empty,
   * not having null in its elements.
   */
  private static boolean checkList(List<?> a) {
    boolean valid = (a != null && !a.isEmpty());
    if (valid) {
      int size = a.size();
      for (int i = 0; valid && i < size; i++) {
        valid = (a.get(i) != null);
      }
    }
    return valid;
  }

  private static ResourceBundle findBundle(CacheKey cacheKey,
      List<Locale> candidateLocales,
      List<String> formats,
      int index,
      Control control,
      ResourceBundle baseBundle) {
    Locale targetLocale = candidateLocales.get(index);
    ResourceBundle parent = null;
    if (index != candidateLocales.size() - 1) {
      parent = findBundle(cacheKey, candidateLocales, formats, index + 1,
          control, baseBundle);
    } else if (baseBundle != null && Locale.ROOT.equals(targetLocale)) {
      return baseBundle;
    }

    // Before we do the real loading work, see whether we need to
    // do some housekeeping: If references to class loaders or
    // resource bundles have been nulled out, remove all related
    // information from the cache.
    Object ref;
    while ((ref = referenceQueue.poll()) != null) {
      cacheList.remove(((CacheKeyReference) ref).getCacheKey());
    }

    // flag indicating the resource bundle has expired in the cache
    boolean expiredBundle = false;

    // First, look up the cache to see if it's in the cache, without
    // attempting to load bundle.
    cacheKey.setLocale(targetLocale);
    ResourceBundle bundle = findBundleInCache(cacheKey, control);
    if (isValidBundle(bundle)) {
      expiredBundle = bundle.expired;
      if (!expiredBundle) {
        // If its parent is the one asked for by the candidate
        // locales (the runtime lookup path), we can take the cached
        // one. (If it's not identical, then we'd have to check the
        // parent's parents to be consistent with what's been
        // requested.)
        if (bundle.parent == parent) {
          return bundle;
        }
        // Otherwise, remove the cached one since we can't keep
        // the same bundles having different parents.
        BundleReference bundleRef = cacheList.get(cacheKey);
        if (bundleRef != null && bundleRef.get() == bundle) {
          cacheList.remove(cacheKey, bundleRef);
        }
      }
    }

    if (bundle != NONEXISTENT_BUNDLE) {
      CacheKey constKey = (CacheKey) cacheKey.clone();

      try {
        bundle = loadBundle(cacheKey, formats, control, expiredBundle);
        if (bundle != null) {
          if (bundle.parent == null) {
            bundle.setParent(parent);
          }
          bundle.locale = targetLocale;
          bundle = putBundleInCache(cacheKey, bundle, control);
          return bundle;
        }

        // Put NONEXISTENT_BUNDLE in the cache as a mark that there's no bundle
        // instance for the locale.
        putBundleInCache(cacheKey, NONEXISTENT_BUNDLE, control);
      } finally {
        if (constKey.getCause() instanceof InterruptedException) {
          Thread.currentThread().interrupt();
        }
      }
    }
    return parent;
  }

  private static ResourceBundle loadBundle(CacheKey cacheKey,
      List<String> formats,
      Control control,
      boolean reload) {

    // Here we actually load the bundle in the order of formats
    // specified by the getFormats() value.
    Locale targetLocale = cacheKey.getLocale();

    ResourceBundle bundle = null;
    int size = formats.size();
    for (int i = 0; i < size; i++) {
      String format = formats.get(i);
      try {
        bundle = control.newBundle(cacheKey.getName(), targetLocale, format,
            cacheKey.getLoader(), reload);
      } catch (LinkageError error) {
        // We need to handle the LinkageError case due to
        // inconsistent case-sensitivity in ClassLoader.
        // See 6572242 for details.
        cacheKey.setCause(error);
      } catch (Exception cause) {
        cacheKey.setCause(cause);
      }
      if (bundle != null) {
        // Set the format in the cache key so that it can be
        // used when calling needsReload later.
        cacheKey.setFormat(format);
        bundle.name = cacheKey.getName();
        bundle.locale = targetLocale;
        // Bundle provider might reuse instances. So we should make
        // sure to clear the expired flag here.
        bundle.expired = false;
        break;
      }
    }

    return bundle;
  }

  private static boolean isValidBundle(ResourceBundle bundle) {
    return bundle != null && bundle != NONEXISTENT_BUNDLE;
  }

  /**
   * Determines whether any of resource bundles in the parent chain,
   * including the leaf, have expired.
   */
  private static boolean hasValidParentChain(ResourceBundle bundle) {
    long now = System.currentTimeMillis();
    while (bundle != null) {
      if (bundle.expired) {
        return false;
      }
      CacheKey key = bundle.cacheKey;
      if (key != null) {
        long expirationTime = key.expirationTime;
        if (expirationTime >= 0 && expirationTime <= now) {
          return false;
        }
      }
      bundle = bundle.parent;
    }
    return true;
  }

  /**
   * Throw a MissingResourceException with proper message
   */
  private static void throwMissingResourceException(String baseName,
      Locale locale,
      Throwable cause) {
    // If the cause is a MissingResourceException, avoid creating
    // a long chain. (6355009)
    if (cause instanceof MissingResourceException) {
      cause = null;
    }
    throw new MissingResourceException("Can't find bundle for base name "
        + baseName + ", locale " + locale,
        baseName + "_" + locale, // className
        "",                      // key
        cause);
  }

  /**
   * Finds a bundle in the cache. Any expired bundles are marked as
   * `expired' and removed from the cache upon return.
   *
   * @param cacheKey the key to look up the cache
   * @param control the Control to be used for the expiration control
   * @return the cached bundle, or null if the bundle is not found in the cache or its parent has
   * expired. <code>bundle.expire</code> is true upon return if the bundle in the cache has
   * expired.
   */
  private static ResourceBundle findBundleInCache(CacheKey cacheKey,
      Control control) {
    BundleReference bundleRef = cacheList.get(cacheKey);
    if (bundleRef == null) {
      return null;
    }
    ResourceBundle bundle = bundleRef.get();
    if (bundle == null) {
      return null;
    }
    ResourceBundle p = bundle.parent;
    assert p != NONEXISTENT_BUNDLE;
    // If the parent has expired, then this one must also expire. We
    // check only the immediate parent because the actual loading is
    // done from the root (base) to leaf (child) and the purpose of
    // checking is to propagate expiration towards the leaf. For
    // example, if the requested locale is ja_JP_JP and there are
    // bundles for all of the candidates in the cache, we have a list,
    //
    // base <- ja <- ja_JP <- ja_JP_JP
    //
    // If ja has expired, then it will reload ja and the list becomes a
    // tree.
    //
    // base <- ja (new)
    //  "   <- ja (expired) <- ja_JP <- ja_JP_JP
    //
    // When looking up ja_JP in the cache, it finds ja_JP in the cache
    // which references to the expired ja. Then, ja_JP is marked as
    // expired and removed from the cache. This will be propagated to
    // ja_JP_JP.
    //
    // Now, it's possible, for example, that while loading new ja_JP,
    // someone else has started loading the same bundle and finds the
    // base bundle has expired. Then, what we get from the first
    // getBundle call includes the expired base bundle. However, if
    // someone else didn't start its loading, we wouldn't know if the
    // base bundle has expired at the end of the loading process. The
    // expiration control doesn't guarantee that the returned bundle and
    // its parents haven't expired.
    //
    // We could check the entire parent chain to see if there's any in
    // the chain that has expired. But this process may never end. An
    // extreme case would be that getTimeToLive returns 0 and
    // needsReload always returns true.
    if (p != null && p.expired) {
      assert bundle != NONEXISTENT_BUNDLE;
      bundle.expired = true;
      bundle.cacheKey = null;
      cacheList.remove(cacheKey, bundleRef);
      bundle = null;
    } else {
      CacheKey key = bundleRef.getCacheKey();
      long expirationTime = key.expirationTime;
      if (!bundle.expired && expirationTime >= 0 &&
          expirationTime <= System.currentTimeMillis()) {
        // its TTL period has expired.
        if (bundle != NONEXISTENT_BUNDLE) {
          // Synchronize here to call needsReload to avoid
          // redundant concurrent calls for the same bundle.
          synchronized (bundle) {
            expirationTime = key.expirationTime;
            if (!bundle.expired && expirationTime >= 0 &&
                expirationTime <= System.currentTimeMillis()) {
              try {
                bundle.expired = control.needsReload(key.getName(),
                    key.getLocale(),
                    key.getFormat(),
                    key.getLoader(),
                    bundle,
                    key.loadTime);
              } catch (Exception e) {
                cacheKey.setCause(e);
              }
              if (bundle.expired) {
                // If the bundle needs to be reloaded, then
                // remove the bundle from the cache, but
                // return the bundle with the expired flag
                // on.
                bundle.cacheKey = null;
                cacheList.remove(cacheKey, bundleRef);
              } else {
                // Update the expiration control info. and reuse
                // the same bundle instance
                setExpirationTime(key, control);
              }
            }
          }
        } else {
          // We just remove NONEXISTENT_BUNDLE from the cache.
          cacheList.remove(cacheKey, bundleRef);
          bundle = null;
        }
      }
    }
    return bundle;
  }

  /**
   * Put a new bundle in the cache.
   *
   * @param cacheKey the key for the resource bundle
   * @param bundle the resource bundle to be put in the cache
   * @return the ResourceBundle for the cacheKey; if someone has put the bundle before this call,
   * the one found in the cache is returned.
   */
  private static ResourceBundle putBundleInCache(CacheKey cacheKey,
      ResourceBundle bundle,
      Control control) {
    setExpirationTime(cacheKey, control);
    if (cacheKey.expirationTime != Control.TTL_DONT_CACHE) {
      CacheKey key = (CacheKey) cacheKey.clone();
      BundleReference bundleRef = new BundleReference(bundle, referenceQueue, key);
      bundle.cacheKey = key;

      // Put the bundle in the cache if it's not been in the cache.
      BundleReference result = cacheList.putIfAbsent(key, bundleRef);

      // If someone else has put the same bundle in the cache before
      // us and it has not expired, we should use the one in the cache.
      if (result != null) {
        ResourceBundle rb = result.get();
        if (rb != null && !rb.expired) {
          // Clear the back link to the cache key
          bundle.cacheKey = null;
          bundle = rb;
          // Clear the reference in the BundleReference so that
          // it won't be enqueued.
          bundleRef.clear();
        } else {
          // Replace the invalid (garbage collected or expired)
          // instance with the valid one.
          cacheList.put(key, bundleRef);
        }
      }
    }
    return bundle;
  }

  private static void setExpirationTime(CacheKey cacheKey, Control control) {
    long ttl = control.getTimeToLive(cacheKey.getName(),
        cacheKey.getLocale());
    if (ttl >= 0) {
      // If any expiration time is specified, set the time to be
      // expired in the cache.
      long now = System.currentTimeMillis();
      cacheKey.loadTime = now;
      cacheKey.expirationTime = now + ttl;
    } else if (ttl >= Control.TTL_NO_EXPIRATION_CONTROL) {
      cacheKey.expirationTime = ttl;
    } else {
      throw new IllegalArgumentException("Invalid Control: TTL=" + ttl);
    }
  }

  /**
   * Removes all resource bundles from the cache that have been loaded
   * using the caller's class loader.
   *
   * @see ResourceBundle.Control#getTimeToLive(String, Locale)
   * @since 1.6
   */
  @CallerSensitive
  public static final void clearCache() {
    clearCache(getLoader(Reflection.getCallerClass()));
  }

  /**
   * Removes all resource bundles from the cache that have been loaded
   * using the given class loader.
   *
   * @param loader the class loader
   * @throws NullPointerException if <code>loader</code> is null
   * @see ResourceBundle.Control#getTimeToLive(String, Locale)
   * @since 1.6
   */
  public static final void clearCache(ClassLoader loader) {
    if (loader == null) {
      throw new NullPointerException();
    }
    Set<CacheKey> set = cacheList.keySet();
    for (CacheKey key : set) {
      if (key.getLoader() == loader) {
        set.remove(key);
      }
    }
  }

  /**
   * Gets an object for the given key from this resource bundle.
   * Returns null if this resource bundle does not contain an
   * object for the given key.
   *
   * @param key the key for the desired object
   * @return the object for the given key, or null
   * @throws NullPointerException if <code>key</code> is <code>null</code>
   */
  protected abstract Object handleGetObject(String key);

  /**
   * Returns an enumeration of the keys.
   *
   * @return an <code>Enumeration</code> of the keys contained in this <code>ResourceBundle</code>
   * and its parent bundles.
   */
  public abstract Enumeration<String> getKeys();

  /**
   * Determines whether the given <code>key</code> is contained in
   * this <code>ResourceBundle</code> or its parent bundles.
   *
   * @param key the resource <code>key</code>
   * @return <code>true</code> if the given <code>key</code> is contained in this
   * <code>ResourceBundle</code> or its parent bundles; <code>false</code> otherwise.
   * @throws NullPointerException if <code>key</code> is <code>null</code>
   * @since 1.6
   */
  public boolean containsKey(String key) {
    if (key == null) {
      throw new NullPointerException();
    }
    for (ResourceBundle rb = this; rb != null; rb = rb.parent) {
      if (rb.handleKeySet().contains(key)) {
        return true;
      }
    }
    return false;
  }

  /**
   * Returns a <code>Set</code> of all keys contained in this
   * <code>ResourceBundle</code> and its parent bundles.
   *
   * @return a <code>Set</code> of all keys contained in this <code>ResourceBundle</code> and its
   * parent bundles.
   * @since 1.6
   */
  public Set<String> keySet() {
    Set<String> keys = new HashSet<>();
    for (ResourceBundle rb = this; rb != null; rb = rb.parent) {
      keys.addAll(rb.handleKeySet());
    }
    return keys;
  }

  /**
   * Returns a <code>Set</code> of the keys contained <em>only</em>
   * in this <code>ResourceBundle</code>.
   *
   * <p>The default implementation returns a <code>Set</code> of the
   * keys returned by the {@link #getKeys() getKeys} method except
   * for the ones for which the {@link #handleGetObject(String)
   * handleGetObject} method returns <code>null</code>. Once the
   * <code>Set</code> has been created, the value is kept in this
   * <code>ResourceBundle</code> in order to avoid producing the
   * same <code>Set</code> in subsequent calls. Subclasses can
   * override this method for faster handling.
   *
   * @return a <code>Set</code> of the keys contained only in this <code>ResourceBundle</code>
   * @since 1.6
   */
  protected Set<String> handleKeySet() {
    if (keySet == null) {
      synchronized (this) {
        if (keySet == null) {
          Set<String> keys = new HashSet<>();
          Enumeration<String> enumKeys = getKeys();
          while (enumKeys.hasMoreElements()) {
            String key = enumKeys.nextElement();
            if (handleGetObject(key) != null) {
              keys.add(key);
            }
          }
          keySet = keys;
        }
      }
    }
    return keySet;
  }


  /**
   * <code>ResourceBundle.Control</code> defines a set of callback methods
   * that are invoked by the {@link ResourceBundle#getBundle(String,
   * Locale, ClassLoader, Control) ResourceBundle.getBundle} factory
   * methods during the bundle loading process. In other words, a
   * <code>ResourceBundle.Control</code> collaborates with the factory
   * methods for loading resource bundles. The default implementation of
   * the callback methods provides the information necessary for the
   * factory methods to perform the <a
   * href="./ResourceBundle.html#default_behavior">default behavior</a>.
   *
   * <p>In addition to the callback methods, the {@link
   * #toBundleName(String, Locale) toBundleName} and {@link
   * #toResourceName(String, String) toResourceName} methods are defined
   * primarily for convenience in implementing the callback
   * methods. However, the <code>toBundleName</code> method could be
   * overridden to provide different conventions in the organization and
   * packaging of localized resources.  The <code>toResourceName</code>
   * method is <code>final</code> to avoid use of wrong resource and class
   * name separators.
   *
   * <p>Two factory methods, {@link #getControl(List)} and {@link
   * #getNoFallbackControl(List)}, provide
   * <code>ResourceBundle.Control</code> instances that implement common
   * variations of the default bundle loading process.
   *
   * <p>The formats returned by the {@link Control#getFormats(String)
   * getFormats} method and candidate locales returned by the {@link
   * ResourceBundle.Control#getCandidateLocales(String, Locale)
   * getCandidateLocales} method must be consistent in all
   * <code>ResourceBundle.getBundle</code> invocations for the same base
   * bundle. Otherwise, the <code>ResourceBundle.getBundle</code> methods
   * may return unintended bundles. For example, if only
   * <code>"java.class"</code> is returned by the <code>getFormats</code>
   * method for the first call to <code>ResourceBundle.getBundle</code>
   * and only <code>"java.properties"</code> for the second call, then the
   * second call will return the class-based one that has been cached
   * during the first call.
   *
   * <p>A <code>ResourceBundle.Control</code> instance must be thread-safe
   * if it's simultaneously used by multiple threads.
   * <code>ResourceBundle.getBundle</code> does not synchronize to call
   * the <code>ResourceBundle.Control</code> methods. The default
   * implementations of the methods are thread-safe.
   *
   * <p>Applications can specify <code>ResourceBundle.Control</code>
   * instances returned by the <code>getControl</code> factory methods or
   * created from a subclass of <code>ResourceBundle.Control</code> to
   * customize the bundle loading process. The following are examples of
   * changing the default bundle loading process.
   *
   * <p><b>Example 1</b>
   *
   * <p>The following code lets <code>ResourceBundle.getBundle</code> look
   * up only properties-based resources.
   *
   * <pre>
   * import java.util.*;
   * import static java.util.ResourceBundle.Control.*;
   * ...
   * ResourceBundle bundle =
   *   ResourceBundle.getBundle("MyResources", new Locale("fr", "CH"),
   *                            ResourceBundle.Control.getControl(FORMAT_PROPERTIES));
   * </pre>
   *
   * Given the resource bundles in the <a
   * href="./ResourceBundle.html#default_behavior_example">example</a> in
   * the <code>ResourceBundle.getBundle</code> description, this
   * <code>ResourceBundle.getBundle</code> call loads
   * <code>MyResources_fr_CH.properties</code> whose parent is
   * <code>MyResources_fr.properties</code> whose parent is
   * <code>MyResources.properties</code>. (<code>MyResources_fr_CH.properties</code>
   * is not hidden, but <code>MyResources_fr_CH.class</code> is.)
   *
   * <p><b>Example 2</b>
   *
   * <p>The following is an example of loading XML-based bundles
   * using {@link Properties#loadFromXML(java.io.InputStream)
   * Properties.loadFromXML}.
   *
   * <pre>
   * ResourceBundle rb = ResourceBundle.getBundle("Messages",
   *     new ResourceBundle.Control() {
   *         public List&lt;String&gt; getFormats(String baseName) {
   *             if (baseName == null)
   *                 throw new NullPointerException();
   *             return Arrays.asList("xml");
   *         }
   *         public ResourceBundle newBundle(String baseName,
   *                                         Locale locale,
   *                                         String format,
   *                                         ClassLoader loader,
   *                                         boolean reload)
   *                          throws IllegalAccessException,
   *                                 InstantiationException,
   *                                 IOException {
   *             if (baseName == null || locale == null
   *                   || format == null || loader == null)
   *                 throw new NullPointerException();
   *             ResourceBundle bundle = null;
   *             if (format.equals("xml")) {
   *                 String bundleName = toBundleName(baseName, locale);
   *                 String resourceName = toResourceName(bundleName, format);
   *                 InputStream stream = null;
   *                 if (reload) {
   *                     URL url = loader.getResource(resourceName);
   *                     if (url != null) {
   *                         URLConnection connection = url.openConnection();
   *                         if (connection != null) {
   *                             // Disable caches to get fresh data for
   *                             // reloading.
   *                             connection.setUseCaches(false);
   *                             stream = connection.getInputStream();
   *                         }
   *                     }
   *                 } else {
   *                     stream = loader.getResourceAsStream(resourceName);
   *                 }
   *                 if (stream != null) {
   *                     BufferedInputStream bis = new BufferedInputStream(stream);
   *                     bundle = new XMLResourceBundle(bis);
   *                     bis.close();
   *                 }
   *             }
   *             return bundle;
   *         }
   *     });
   *
   * ...
   *
   * private static class XMLResourceBundle extends ResourceBundle {
   *     private Properties props;
   *     XMLResourceBundle(InputStream stream) throws IOException {
   *         props = new Properties();
   *         props.loadFromXML(stream);
   *     }
   *     protected Object handleGetObject(String key) {
   *         return props.getProperty(key);
   *     }
   *     public Enumeration&lt;String&gt; getKeys() {
   *         ...
   *     }
   * }
   * </pre>
   *
   * @since 1.6
   */
  public static class Control {

    /**
     * The default format <code>List</code>, which contains the strings
     * <code>"java.class"</code> and <code>"java.properties"</code>, in
     * this order. This <code>List</code> is {@linkplain
     * Collections#unmodifiableList(List) unmodifiable}.
     *
     * @see #getFormats(String)
     */
    public static final List<String> FORMAT_DEFAULT
        = Collections.unmodifiableList(Arrays.asList("java.class",
        "java.properties"));

    /**
     * The class-only format <code>List</code> containing
     * <code>"java.class"</code>. This <code>List</code> is {@linkplain
     * Collections#unmodifiableList(List) unmodifiable}.
     *
     * @see #getFormats(String)
     */
    public static final List<String> FORMAT_CLASS
        = Collections.unmodifiableList(Arrays.asList("java.class"));

    /**
     * The properties-only format <code>List</code> containing
     * <code>"java.properties"</code>. This <code>List</code> is
     * {@linkplain Collections#unmodifiableList(List) unmodifiable}.
     *
     * @see #getFormats(String)
     */
    public static final List<String> FORMAT_PROPERTIES
        = Collections.unmodifiableList(Arrays.asList("java.properties"));

    /**
     * The time-to-live constant for not caching loaded resource bundle
     * instances.
     *
     * @see #getTimeToLive(String, Locale)
     */
    public static final long TTL_DONT_CACHE = -1;

    /**
     * The time-to-live constant for disabling the expiration control
     * for loaded resource bundle instances in the cache.
     *
     * @see #getTimeToLive(String, Locale)
     */
    public static final long TTL_NO_EXPIRATION_CONTROL = -2;

    private static final Control INSTANCE = new Control();

    /**
     * Sole constructor. (For invocation by subclass constructors,
     * typically implicit.)
     */
    protected Control() {
    }

    /**
     * Returns a <code>ResourceBundle.Control</code> in which the {@link
     * #getFormats(String) getFormats} method returns the specified
     * <code>formats</code>. The <code>formats</code> must be equal to
     * one of {@link Control#FORMAT_PROPERTIES}, {@link
     * Control#FORMAT_CLASS} or {@link
     * Control#FORMAT_DEFAULT}. <code>ResourceBundle.Control</code>
     * instances returned by this method are singletons and thread-safe.
     *
     * <p>Specifying {@link Control#FORMAT_DEFAULT} is equivalent to
     * instantiating the <code>ResourceBundle.Control</code> class,
     * except that this method returns a singleton.
     *
     * @param formats the formats to be returned by the <code>ResourceBundle.Control.getFormats</code>
     * method
     * @return a <code>ResourceBundle.Control</code> supporting the specified <code>formats</code>
     * @throws NullPointerException if <code>formats</code> is <code>null</code>
     * @throws IllegalArgumentException if <code>formats</code> is unknown
     */
    public static final Control getControl(List<String> formats) {
      if (formats.equals(Control.FORMAT_PROPERTIES)) {
        return SingleFormatControl.PROPERTIES_ONLY;
      }
      if (formats.equals(Control.FORMAT_CLASS)) {
        return SingleFormatControl.CLASS_ONLY;
      }
      if (formats.equals(Control.FORMAT_DEFAULT)) {
        return Control.INSTANCE;
      }
      throw new IllegalArgumentException();
    }

    /**
     * Returns a <code>ResourceBundle.Control</code> in which the {@link
     * #getFormats(String) getFormats} method returns the specified
     * <code>formats</code> and the {@link
     * Control#getFallbackLocale(String, Locale) getFallbackLocale}
     * method returns <code>null</code>. The <code>formats</code> must
     * be equal to one of {@link Control#FORMAT_PROPERTIES}, {@link
     * Control#FORMAT_CLASS} or {@link Control#FORMAT_DEFAULT}.
     * <code>ResourceBundle.Control</code> instances returned by this
     * method are singletons and thread-safe.
     *
     * @param formats the formats to be returned by the <code>ResourceBundle.Control.getFormats</code>
     * method
     * @return a <code>ResourceBundle.Control</code> supporting the specified <code>formats</code>
     * with no fallback <code>Locale</code> support
     * @throws NullPointerException if <code>formats</code> is <code>null</code>
     * @throws IllegalArgumentException if <code>formats</code> is unknown
     */
    public static final Control getNoFallbackControl(List<String> formats) {
      if (formats.equals(Control.FORMAT_DEFAULT)) {
        return NoFallbackControl.NO_FALLBACK;
      }
      if (formats.equals(Control.FORMAT_PROPERTIES)) {
        return NoFallbackControl.PROPERTIES_ONLY_NO_FALLBACK;
      }
      if (formats.equals(Control.FORMAT_CLASS)) {
        return NoFallbackControl.CLASS_ONLY_NO_FALLBACK;
      }
      throw new IllegalArgumentException();
    }

    /**
     * Returns a <code>List</code> of <code>String</code>s containing
     * formats to be used to load resource bundles for the given
     * <code>baseName</code>. The <code>ResourceBundle.getBundle</code>
     * factory method tries to load resource bundles with formats in the
     * order specified by the list. The list returned by this method
     * must have at least one <code>String</code>. The predefined
     * formats are <code>"java.class"</code> for class-based resource
     * bundles and <code>"java.properties"</code> for {@linkplain
     * PropertyResourceBundle properties-based} ones. Strings starting
     * with <code>"java."</code> are reserved for future extensions and
     * must not be used by application-defined formats.
     *
     * <p>It is not a requirement to return an immutable (unmodifiable)
     * <code>List</code>.  However, the returned <code>List</code> must
     * not be mutated after it has been returned by
     * <code>getFormats</code>.
     *
     * <p>The default implementation returns {@link #FORMAT_DEFAULT} so
     * that the <code>ResourceBundle.getBundle</code> factory method
     * looks up first class-based resource bundles, then
     * properties-based ones.
     *
     * @param baseName the base name of the resource bundle, a fully qualified class name
     * @return a <code>List</code> of <code>String</code>s containing formats for loading resource
     * bundles.
     * @throws NullPointerException if <code>baseName</code> is null
     * @see #FORMAT_DEFAULT
     * @see #FORMAT_CLASS
     * @see #FORMAT_PROPERTIES
     */
    public List<String> getFormats(String baseName) {
      if (baseName == null) {
        throw new NullPointerException();
      }
      return FORMAT_DEFAULT;
    }

    /**
     * Returns a <code>List</code> of <code>Locale</code>s as candidate
     * locales for <code>baseName</code> and <code>locale</code>. This
     * method is called by the <code>ResourceBundle.getBundle</code>
     * factory method each time the factory method tries finding a
     * resource bundle for a target <code>Locale</code>.
     *
     * <p>The sequence of the candidate locales also corresponds to the
     * runtime resource lookup path (also known as the <I>parent
     * chain</I>), if the corresponding resource bundles for the
     * candidate locales exist and their parents are not defined by
     * loaded resource bundles themselves.  The last element of the list
     * must be a {@linkplain Locale#ROOT root locale} if it is desired to
     * have the base bundle as the terminal of the parent chain.
     *
     * <p>If the given locale is equal to <code>Locale.ROOT</code> (the
     * root locale), a <code>List</code> containing only the root
     * <code>Locale</code> must be returned. In this case, the
     * <code>ResourceBundle.getBundle</code> factory method loads only
     * the base bundle as the resulting resource bundle.
     *
     * <p>It is not a requirement to return an immutable (unmodifiable)
     * <code>List</code>. However, the returned <code>List</code> must not
     * be mutated after it has been returned by
     * <code>getCandidateLocales</code>.
     *
     * <p>The default implementation returns a <code>List</code> containing
     * <code>Locale</code>s using the rules described below.  In the
     * description below, <em>L</em>, <em>S</em>, <em>C</em> and <em>V</em>
     * respectively represent non-empty language, script, country, and
     * variant.  For example, [<em>L</em>, <em>C</em>] represents a
     * <code>Locale</code> that has non-empty values only for language and
     * country.  The form <em>L</em>("xx") represents the (non-empty)
     * language value is "xx".  For all cases, <code>Locale</code>s whose
     * final component values are empty strings are omitted.
     *
     * <ol><li>For an input <code>Locale</code> with an empty script value,
     * append candidate <code>Locale</code>s by omitting the final component
     * one by one as below:
     *
     * <ul>
     * <li> [<em>L</em>, <em>C</em>, <em>V</em>] </li>
     * <li> [<em>L</em>, <em>C</em>] </li>
     * <li> [<em>L</em>] </li>
     * <li> <code>Locale.ROOT</code> </li>
     * </ul></li>
     *
     * <li>For an input <code>Locale</code> with a non-empty script value,
     * append candidate <code>Locale</code>s by omitting the final component
     * up to language, then append candidates generated from the
     * <code>Locale</code> with country and variant restored:
     *
     * <ul>
     * <li> [<em>L</em>, <em>S</em>, <em>C</em>, <em>V</em>]</li>
     * <li> [<em>L</em>, <em>S</em>, <em>C</em>]</li>
     * <li> [<em>L</em>, <em>S</em>]</li>
     * <li> [<em>L</em>, <em>C</em>, <em>V</em>]</li>
     * <li> [<em>L</em>, <em>C</em>]</li>
     * <li> [<em>L</em>]</li>
     * <li> <code>Locale.ROOT</code></li>
     * </ul></li>
     *
     * <li>For an input <code>Locale</code> with a variant value consisting
     * of multiple subtags separated by underscore, generate candidate
     * <code>Locale</code>s by omitting the variant subtags one by one, then
     * insert them after every occurrence of <code> Locale</code>s with the
     * full variant value in the original list.  For example, if the
     * the variant consists of two subtags <em>V1</em> and <em>V2</em>:
     *
     * <ul>
     * <li> [<em>L</em>, <em>S</em>, <em>C</em>, <em>V1</em>, <em>V2</em>]</li>
     * <li> [<em>L</em>, <em>S</em>, <em>C</em>, <em>V1</em>]</li>
     * <li> [<em>L</em>, <em>S</em>, <em>C</em>]</li>
     * <li> [<em>L</em>, <em>S</em>]</li>
     * <li> [<em>L</em>, <em>C</em>, <em>V1</em>, <em>V2</em>]</li>
     * <li> [<em>L</em>, <em>C</em>, <em>V1</em>]</li>
     * <li> [<em>L</em>, <em>C</em>]</li>
     * <li> [<em>L</em>]</li>
     * <li> <code>Locale.ROOT</code></li>
     * </ul></li>
     *
     * <li>Special cases for Chinese.  When an input <code>Locale</code> has the
     * language "zh" (Chinese) and an empty script value, either "Hans" (Simplified) or
     * "Hant" (Traditional) might be supplied, depending on the country.
     * When the country is "CN" (China) or "SG" (Singapore), "Hans" is supplied.
     * When the country is "HK" (Hong Kong SAR China), "MO" (Macau SAR China),
     * or "TW" (Taiwan), "Hant" is supplied.  For all other countries or when the country
     * is empty, no script is supplied.  For example, for <code>Locale("zh", "CN")
     * </code>, the candidate list will be:
     * <ul>
     * <li> [<em>L</em>("zh"), <em>S</em>("Hans"), <em>C</em>("CN")]</li>
     * <li> [<em>L</em>("zh"), <em>S</em>("Hans")]</li>
     * <li> [<em>L</em>("zh"), <em>C</em>("CN")]</li>
     * <li> [<em>L</em>("zh")]</li>
     * <li> <code>Locale.ROOT</code></li>
     * </ul>
     *
     * For <code>Locale("zh", "TW")</code>, the candidate list will be:
     * <ul>
     * <li> [<em>L</em>("zh"), <em>S</em>("Hant"), <em>C</em>("TW")]</li>
     * <li> [<em>L</em>("zh"), <em>S</em>("Hant")]</li>
     * <li> [<em>L</em>("zh"), <em>C</em>("TW")]</li>
     * <li> [<em>L</em>("zh")]</li>
     * <li> <code>Locale.ROOT</code></li>
     * </ul></li>
     *
     * <li>Special cases for Norwegian.  Both <code>Locale("no", "NO",
     * "NY")</code> and <code>Locale("nn", "NO")</code> represent Norwegian
     * Nynorsk.  When a locale's language is "nn", the standard candidate
     * list is generated up to [<em>L</em>("nn")], and then the following
     * candidates are added:
     *
     * <ul><li> [<em>L</em>("no"), <em>C</em>("NO"), <em>V</em>("NY")]</li>
     * <li> [<em>L</em>("no"), <em>C</em>("NO")]</li>
     * <li> [<em>L</em>("no")]</li>
     * <li> <code>Locale.ROOT</code></li>
     * </ul>
     *
     * If the locale is exactly <code>Locale("no", "NO", "NY")</code>, it is first
     * converted to <code>Locale("nn", "NO")</code> and then the above procedure is
     * followed.
     *
     * <p>Also, Java treats the language "no" as a synonym of Norwegian
     * Bokm&#xE5;l "nb".  Except for the single case <code>Locale("no",
     * "NO", "NY")</code> (handled above), when an input <code>Locale</code>
     * has language "no" or "nb", candidate <code>Locale</code>s with
     * language code "no" and "nb" are interleaved, first using the
     * requested language, then using its synonym. For example,
     * <code>Locale("nb", "NO", "POSIX")</code> generates the following
     * candidate list:
     *
     * <ul>
     * <li> [<em>L</em>("nb"), <em>C</em>("NO"), <em>V</em>("POSIX")]</li>
     * <li> [<em>L</em>("no"), <em>C</em>("NO"), <em>V</em>("POSIX")]</li>
     * <li> [<em>L</em>("nb"), <em>C</em>("NO")]</li>
     * <li> [<em>L</em>("no"), <em>C</em>("NO")]</li>
     * <li> [<em>L</em>("nb")]</li>
     * <li> [<em>L</em>("no")]</li>
     * <li> <code>Locale.ROOT</code></li>
     * </ul>
     *
     * <code>Locale("no", "NO", "POSIX")</code> would generate the same list
     * except that locales with "no" would appear before the corresponding
     * locales with "nb".</li>
     * </ol>
     *
     * <p>The default implementation uses an {@link ArrayList} that
     * overriding implementations may modify before returning it to the
     * caller. However, a subclass must not modify it after it has
     * been returned by <code>getCandidateLocales</code>.
     *
     * <p>For example, if the given <code>baseName</code> is "Messages"
     * and the given <code>locale</code> is
     * <code>Locale("ja",&nbsp;"",&nbsp;"XX")</code>, then a
     * <code>List</code> of <code>Locale</code>s:
     * <pre>
     *     Locale("ja", "", "XX")
     *     Locale("ja")
     *     Locale.ROOT
     * </pre>
     * is returned. And if the resource bundles for the "ja" and
     * "" <code>Locale</code>s are found, then the runtime resource
     * lookup path (parent chain) is:
     * <pre>{@code
     *     Messages_ja -> Messages
     * }</pre>
     *
     * @param baseName the base name of the resource bundle, a fully qualified class name
     * @param locale the locale for which a resource bundle is desired
     * @return a <code>List</code> of candidate <code>Locale</code>s for the given
     * <code>locale</code>
     * @throws NullPointerException if <code>baseName</code> or <code>locale</code> is
     * <code>null</code>
     */
    public List<Locale> getCandidateLocales(String baseName, Locale locale) {
      if (baseName == null) {
        throw new NullPointerException();
      }
      return new ArrayList<>(CANDIDATES_CACHE.get(locale.getBaseLocale()));
    }

    private static final CandidateListCache CANDIDATES_CACHE = new CandidateListCache();

    private static class CandidateListCache extends LocaleObjectCache<BaseLocale, List<Locale>> {

      protected List<Locale> createObject(BaseLocale base) {
        String language = base.getLanguage();
        String script = base.getScript();
        String region = base.getRegion();
        String variant = base.getVariant();

        // Special handling for Norwegian
        boolean isNorwegianBokmal = false;
        boolean isNorwegianNynorsk = false;
        if (language.equals("no")) {
          if (region.equals("NO") && variant.equals("NY")) {
            variant = "";
            isNorwegianNynorsk = true;
          } else {
            isNorwegianBokmal = true;
          }
        }
        if (language.equals("nb") || isNorwegianBokmal) {
          List<Locale> tmpList = getDefaultList("nb", script, region, variant);
          // Insert a locale replacing "nb" with "no" for every list entry
          List<Locale> bokmalList = new LinkedList<>();
          for (Locale l : tmpList) {
            bokmalList.add(l);
            if (l.getLanguage().length() == 0) {
              break;
            }
            bokmalList.add(Locale.getInstance("no", l.getScript(), l.getCountry(),
                l.getVariant(), null));
          }
          return bokmalList;
        } else if (language.equals("nn") || isNorwegianNynorsk) {
          // Insert no_NO_NY, no_NO, no after nn
          List<Locale> nynorskList = getDefaultList("nn", script, region, variant);
          int idx = nynorskList.size() - 1;
          nynorskList.add(idx++, Locale.getInstance("no", "NO", "NY"));
          nynorskList.add(idx++, Locale.getInstance("no", "NO", ""));
          nynorskList.add(idx++, Locale.getInstance("no", "", ""));
          return nynorskList;
        }
        // Special handling for Chinese
        else if (language.equals("zh")) {
          if (script.length() == 0 && region.length() > 0) {
            // Supply script for users who want to use zh_Hans/zh_Hant
            // as bundle names (recommended for Java7+)
            switch (region) {
              case "TW":
              case "HK":
              case "MO":
                script = "Hant";
                break;
              case "CN":
              case "SG":
                script = "Hans";
                break;
            }
          } else if (script.length() > 0 && region.length() == 0) {
            // Supply region(country) for users who still package Chinese
            // bundles using old convension.
            switch (script) {
              case "Hans":
                region = "CN";
                break;
              case "Hant":
                region = "TW";
                break;
            }
          }
        }

        return getDefaultList(language, script, region, variant);
      }

      private static List<Locale> getDefaultList(String language, String script, String region,
          String variant) {
        List<String> variants = null;

        if (variant.length() > 0) {
          variants = new LinkedList<>();
          int idx = variant.length();
          while (idx != -1) {
            variants.add(variant.substring(0, idx));
            idx = variant.lastIndexOf('_', --idx);
          }
        }

        List<Locale> list = new LinkedList<>();

        if (variants != null) {
          for (String v : variants) {
            list.add(Locale.getInstance(language, script, region, v, null));
          }
        }
        if (region.length() > 0) {
          list.add(Locale.getInstance(language, script, region, "", null));
        }
        if (script.length() > 0) {
          list.add(Locale.getInstance(language, script, "", "", null));

          // With script, after truncating variant, region and script,
          // start over without script.
          if (variants != null) {
            for (String v : variants) {
              list.add(Locale.getInstance(language, "", region, v, null));
            }
          }
          if (region.length() > 0) {
            list.add(Locale.getInstance(language, "", region, "", null));
          }
        }
        if (language.length() > 0) {
          list.add(Locale.getInstance(language, "", "", "", null));
        }
        // Add root locale at the end
        list.add(Locale.ROOT);

        return list;
      }
    }

    /**
     * Returns a <code>Locale</code> to be used as a fallback locale for
     * further resource bundle searches by the
     * <code>ResourceBundle.getBundle</code> factory method. This method
     * is called from the factory method every time when no resulting
     * resource bundle has been found for <code>baseName</code> and
     * <code>locale</code>, where locale is either the parameter for
     * <code>ResourceBundle.getBundle</code> or the previous fallback
     * locale returned by this method.
     *
     * <p>The method returns <code>null</code> if no further fallback
     * search is desired.
     *
     * <p>The default implementation returns the {@linkplain
     * Locale#getDefault() default <code>Locale</code>} if the given
     * <code>locale</code> isn't the default one.  Otherwise,
     * <code>null</code> is returned.
     *
     * @param baseName the base name of the resource bundle, a fully qualified class name for which
     * <code>ResourceBundle.getBundle</code> has been unable to find any resource bundles (except
     * for the base bundle)
     * @param locale the <code>Locale</code> for which <code>ResourceBundle.getBundle</code> has
     * been unable to find any resource bundles (except for the base bundle)
     * @return a <code>Locale</code> for the fallback search, or <code>null</code> if no further
     * fallback search is desired.
     * @throws NullPointerException if <code>baseName</code> or <code>locale</code> is
     * <code>null</code>
     */
    public Locale getFallbackLocale(String baseName, Locale locale) {
      if (baseName == null) {
        throw new NullPointerException();
      }
      Locale defaultLocale = Locale.getDefault();
      return locale.equals(defaultLocale) ? null : defaultLocale;
    }

    /**
     * Instantiates a resource bundle for the given bundle name of the
     * given format and locale, using the given class loader if
     * necessary. This method returns <code>null</code> if there is no
     * resource bundle available for the given parameters. If a resource
     * bundle can't be instantiated due to an unexpected error, the
     * error must be reported by throwing an <code>Error</code> or
     * <code>Exception</code> rather than simply returning
     * <code>null</code>.
     *
     * <p>If the <code>reload</code> flag is <code>true</code>, it
     * indicates that this method is being called because the previously
     * loaded resource bundle has expired.
     *
     * <p>The default implementation instantiates a
     * <code>ResourceBundle</code> as follows.
     *
     * <ul>
     *
     * <li>The bundle name is obtained by calling {@link
     * #toBundleName(String, Locale) toBundleName(baseName,
     * locale)}.</li>
     *
     * <li>If <code>format</code> is <code>"java.class"</code>, the
     * {@link Class} specified by the bundle name is loaded by calling
     * {@link ClassLoader#loadClass(String)}. Then, a
     * <code>ResourceBundle</code> is instantiated by calling {@link
     * Class#newInstance()}.  Note that the <code>reload</code> flag is
     * ignored for loading class-based resource bundles in this default
     * implementation.</li>
     *
     * <li>If <code>format</code> is <code>"java.properties"</code>,
     * {@link #toResourceName(String, String) toResourceName(bundlename,
     * "properties")} is called to get the resource name.
     * If <code>reload</code> is <code>true</code>, {@link
     * ClassLoader#getResource(String) load.getResource} is called
     * to get a {@link URL} for creating a {@link
     * URLConnection}. This <code>URLConnection</code> is used to
     * {@linkplain URLConnection#setUseCaches(boolean) disable the
     * caches} of the underlying resource loading layers,
     * and to {@linkplain URLConnection#getInputStream() get an
     * <code>InputStream</code>}.
     * Otherwise, {@link ClassLoader#getResourceAsStream(String)
     * loader.getResourceAsStream} is called to get an {@link
     * InputStream}. Then, a {@link
     * PropertyResourceBundle} is constructed with the
     * <code>InputStream</code>.</li>
     *
     * <li>If <code>format</code> is neither <code>"java.class"</code>
     * nor <code>"java.properties"</code>, an
     * <code>IllegalArgumentException</code> is thrown.</li>
     *
     * </ul>
     *
     * @param baseName the base bundle name of the resource bundle, a fully qualified class name
     * @param locale the locale for which the resource bundle should be instantiated
     * @param format the resource bundle format to be loaded
     * @param loader the <code>ClassLoader</code> to use to load the bundle
     * @param reload the flag to indicate bundle reloading; <code>true</code> if reloading an
     * expired resource bundle, <code>false</code> otherwise
     * @return the resource bundle instance, or <code>null</code> if none could be found.
     * @throws NullPointerException if <code>bundleName</code>, <code>locale</code>,
     * <code>format</code>, or <code>loader</code> is <code>null</code>, or if <code>null</code> is
     * returned by {@link #toBundleName(String, Locale) toBundleName}
     * @throws IllegalArgumentException if <code>format</code> is unknown, or if the resource found
     * for the given parameters contains malformed data.
     * @throws ClassCastException if the loaded class cannot be cast to <code>ResourceBundle</code>
     * @throws IllegalAccessException if the class or its nullary constructor is not accessible.
     * @throws InstantiationException if the instantiation of a class fails for some other reason.
     * @throws ExceptionInInitializerError if the initialization provoked by this method fails.
     * @throws SecurityException If a security manager is present and creation of new instances is
     * denied. See {@link Class#newInstance()} for details.
     * @throws IOException if an error occurred when reading resources using any I/O operations
     */
    public ResourceBundle newBundle(String baseName, Locale locale, String format,
        ClassLoader loader, boolean reload)
        throws IllegalAccessException, InstantiationException, IOException {
      String bundleName = toBundleName(baseName, locale);
      ResourceBundle bundle = null;
      if (format.equals("java.class")) {
        try {
          @SuppressWarnings("unchecked")
          Class<? extends ResourceBundle> bundleClass
              = (Class<? extends ResourceBundle>) loader.loadClass(bundleName);

          // If the class isn't a ResourceBundle subclass, throw a
          // ClassCastException.
          if (ResourceBundle.class.isAssignableFrom(bundleClass)) {
            bundle = bundleClass.newInstance();
          } else {
            throw new ClassCastException(bundleClass.getName()
                + " cannot be cast to ResourceBundle");
          }
        } catch (ClassNotFoundException e) {
        }
      } else if (format.equals("java.properties")) {
        final String resourceName = toResourceName0(bundleName, "properties");
        if (resourceName == null) {
          return bundle;
        }
        final ClassLoader classLoader = loader;
        final boolean reloadFlag = reload;
        InputStream stream = null;
        try {
          stream = AccessController.doPrivileged(
              new PrivilegedExceptionAction<InputStream>() {
                public InputStream run() throws IOException {
                  InputStream is = null;
                  if (reloadFlag) {
                    URL url = classLoader.getResource(resourceName);
                    if (url != null) {
                      URLConnection connection = url.openConnection();
                      if (connection != null) {
                        // Disable caches to get fresh data for
                        // reloading.
                        connection.setUseCaches(false);
                        is = connection.getInputStream();
                      }
                    }
                  } else {
                    is = classLoader.getResourceAsStream(resourceName);
                  }
                  return is;
                }
              });
        } catch (PrivilegedActionException e) {
          throw (IOException) e.getException();
        }
        if (stream != null) {
          try {
            bundle = new PropertyResourceBundle(stream);
          } finally {
            stream.close();
          }
        }
      } else {
        throw new IllegalArgumentException("unknown format: " + format);
      }
      return bundle;
    }

    /**
     * Returns the time-to-live (TTL) value for resource bundles that
     * are loaded under this
     * <code>ResourceBundle.Control</code>. Positive time-to-live values
     * specify the number of milliseconds a bundle can remain in the
     * cache without being validated against the source data from which
     * it was constructed. The value 0 indicates that a bundle must be
     * validated each time it is retrieved from the cache. {@link
     * #TTL_DONT_CACHE} specifies that loaded resource bundles are not
     * put in the cache. {@link #TTL_NO_EXPIRATION_CONTROL} specifies
     * that loaded resource bundles are put in the cache with no
     * expiration control.
     *
     * <p>The expiration affects only the bundle loading process by the
     * <code>ResourceBundle.getBundle</code> factory method.  That is,
     * if the factory method finds a resource bundle in the cache that
     * has expired, the factory method calls the {@link
     * #needsReload(String, Locale, String, ClassLoader, ResourceBundle,
     * long) needsReload} method to determine whether the resource
     * bundle needs to be reloaded. If <code>needsReload</code> returns
     * <code>true</code>, the cached resource bundle instance is removed
     * from the cache. Otherwise, the instance stays in the cache,
     * updated with the new TTL value returned by this method.
     *
     * <p>All cached resource bundles are subject to removal from the
     * cache due to memory constraints of the runtime environment.
     * Returning a large positive value doesn't mean to lock loaded
     * resource bundles in the cache.
     *
     * <p>The default implementation returns {@link #TTL_NO_EXPIRATION_CONTROL}.
     *
     * @param baseName the base name of the resource bundle for which the expiration value is
     * specified.
     * @param locale the locale of the resource bundle for which the expiration value is specified.
     * @return the time (0 or a positive millisecond offset from the cached time) to get loaded
     * bundles expired in the cache, {@link #TTL_NO_EXPIRATION_CONTROL} to disable the expiration
     * control, or {@link #TTL_DONT_CACHE} to disable caching.
     * @throws NullPointerException if <code>baseName</code> or <code>locale</code> is
     * <code>null</code>
     */
    public long getTimeToLive(String baseName, Locale locale) {
      if (baseName == null || locale == null) {
        throw new NullPointerException();
      }
      return TTL_NO_EXPIRATION_CONTROL;
    }

    /**
     * Determines if the expired <code>bundle</code> in the cache needs
     * to be reloaded based on the loading time given by
     * <code>loadTime</code> or some other criteria. The method returns
     * <code>true</code> if reloading is required; <code>false</code>
     * otherwise. <code>loadTime</code> is a millisecond offset since
     * the <a href="Calendar.html#Epoch"> <code>Calendar</code>
     * Epoch</a>.
     *
     * The calling <code>ResourceBundle.getBundle</code> factory method
     * calls this method on the <code>ResourceBundle.Control</code>
     * instance used for its current invocation, not on the instance
     * used in the invocation that originally loaded the resource
     * bundle.
     *
     * <p>The default implementation compares <code>loadTime</code> and
     * the last modified time of the source data of the resource
     * bundle. If it's determined that the source data has been modified
     * since <code>loadTime</code>, <code>true</code> is
     * returned. Otherwise, <code>false</code> is returned. This
     * implementation assumes that the given <code>format</code> is the
     * same string as its file suffix if it's not one of the default
     * formats, <code>"java.class"</code> or
     * <code>"java.properties"</code>.
     *
     * @param baseName the base bundle name of the resource bundle, a fully qualified class name
     * @param locale the locale for which the resource bundle should be instantiated
     * @param format the resource bundle format to be loaded
     * @param loader the <code>ClassLoader</code> to use to load the bundle
     * @param bundle the resource bundle instance that has been expired in the cache
     * @param loadTime the time when <code>bundle</code> was loaded and put in the cache
     * @return <code>true</code> if the expired bundle needs to be reloaded; <code>false</code>
     * otherwise.
     * @throws NullPointerException if <code>baseName</code>, <code>locale</code>,
     * <code>format</code>, <code>loader</code>, or <code>bundle</code> is <code>null</code>
     */
    public boolean needsReload(String baseName, Locale locale,
        String format, ClassLoader loader,
        ResourceBundle bundle, long loadTime) {
      if (bundle == null) {
        throw new NullPointerException();
      }
      if (format.equals("java.class") || format.equals("java.properties")) {
        format = format.substring(5);
      }
      boolean result = false;
      try {
        String resourceName = toResourceName0(toBundleName(baseName, locale), format);
        if (resourceName == null) {
          return result;
        }
        URL url = loader.getResource(resourceName);
        if (url != null) {
          long lastModified = 0;
          URLConnection connection = url.openConnection();
          if (connection != null) {
            // disable caches to get the correct data
            connection.setUseCaches(false);
            if (connection instanceof JarURLConnection) {
              JarEntry ent = ((JarURLConnection) connection).getJarEntry();
              if (ent != null) {
                lastModified = ent.getTime();
                if (lastModified == -1) {
                  lastModified = 0;
                }
              }
            } else {
              lastModified = connection.getLastModified();
            }
          }
          result = lastModified >= loadTime;
        }
      } catch (NullPointerException npe) {
        throw npe;
      } catch (Exception e) {
        // ignore other exceptions
      }
      return result;
    }

    /**
     * Converts the given <code>baseName</code> and <code>locale</code>
     * to the bundle name. This method is called from the default
     * implementation of the {@link #newBundle(String, Locale, String,
     * ClassLoader, boolean) newBundle} and {@link #needsReload(String,
     * Locale, String, ClassLoader, ResourceBundle, long) needsReload}
     * methods.
     *
     * <p>This implementation returns the following value:
     * <pre>
     *     baseName + "_" + language + "_" + script + "_" + country + "_" + variant
     * </pre>
     * where <code>language</code>, <code>script</code>, <code>country</code>,
     * and <code>variant</code> are the language, script, country, and variant
     * values of <code>locale</code>, respectively. Final component values that
     * are empty Strings are omitted along with the preceding '_'.  When the
     * script is empty, the script value is omitted along with the preceding '_'.
     * If all of the values are empty strings, then <code>baseName</code>
     * is returned.
     *
     * <p>For example, if <code>baseName</code> is
     * <code>"baseName"</code> and <code>locale</code> is
     * <code>Locale("ja",&nbsp;"",&nbsp;"XX")</code>, then
     * <code>"baseName_ja_&thinsp;_XX"</code> is returned. If the given
     * locale is <code>Locale("en")</code>, then
     * <code>"baseName_en"</code> is returned.
     *
     * <p>Overriding this method allows applications to use different
     * conventions in the organization and packaging of localized
     * resources.
     *
     * @param baseName the base name of the resource bundle, a fully qualified class name
     * @param locale the locale for which a resource bundle should be loaded
     * @return the bundle name for the resource bundle
     * @throws NullPointerException if <code>baseName</code> or <code>locale</code> is
     * <code>null</code>
     */
    public String toBundleName(String baseName, Locale locale) {
      if (locale == Locale.ROOT) {
        return baseName;
      }

      String language = locale.getLanguage();
      String script = locale.getScript();
      String country = locale.getCountry();
      String variant = locale.getVariant();

      if (language == "" && country == "" && variant == "") {
        return baseName;
      }

      StringBuilder sb = new StringBuilder(baseName);
      sb.append('_');
      if (script != "") {
        if (variant != "") {
          sb.append(language).append('_').append(script).append('_').append(country).append('_')
              .append(variant);
        } else if (country != "") {
          sb.append(language).append('_').append(script).append('_').append(country);
        } else {
          sb.append(language).append('_').append(script);
        }
      } else {
        if (variant != "") {
          sb.append(language).append('_').append(country).append('_').append(variant);
        } else if (country != "") {
          sb.append(language).append('_').append(country);
        } else {
          sb.append(language);
        }
      }
      return sb.toString();

    }

    /**
     * Converts the given <code>bundleName</code> to the form required
     * by the {@link ClassLoader#getResource ClassLoader.getResource}
     * method by replacing all occurrences of <code>'.'</code> in
     * <code>bundleName</code> with <code>'/'</code> and appending a
     * <code>'.'</code> and the given file <code>suffix</code>. For
     * example, if <code>bundleName</code> is
     * <code>"foo.bar.MyResources_ja_JP"</code> and <code>suffix</code>
     * is <code>"properties"</code>, then
     * <code>"foo/bar/MyResources_ja_JP.properties"</code> is returned.
     *
     * @param bundleName the bundle name
     * @param suffix the file type suffix
     * @return the converted resource name
     * @throws NullPointerException if <code>bundleName</code> or <code>suffix</code> is
     * <code>null</code>
     */
    public final String toResourceName(String bundleName, String suffix) {
      StringBuilder sb = new StringBuilder(bundleName.length() + 1 + suffix.length());
      sb.append(bundleName.replace('.', '/')).append('.').append(suffix);
      return sb.toString();
    }

    private String toResourceName0(String bundleName, String suffix) {
      // application protocol check
      if (bundleName.contains("://")) {
        return null;
      } else {
        return toResourceName(bundleName, suffix);
      }
    }
  }

  private static class SingleFormatControl extends Control {

    private static final Control PROPERTIES_ONLY
        = new SingleFormatControl(FORMAT_PROPERTIES);

    private static final Control CLASS_ONLY
        = new SingleFormatControl(FORMAT_CLASS);

    private final List<String> formats;

    protected SingleFormatControl(List<String> formats) {
      this.formats = formats;
    }

    public List<String> getFormats(String baseName) {
      if (baseName == null) {
        throw new NullPointerException();
      }
      return formats;
    }
  }

  private static final class NoFallbackControl extends SingleFormatControl {

    private static final Control NO_FALLBACK
        = new NoFallbackControl(FORMAT_DEFAULT);

    private static final Control PROPERTIES_ONLY_NO_FALLBACK
        = new NoFallbackControl(FORMAT_PROPERTIES);

    private static final Control CLASS_ONLY_NO_FALLBACK
        = new NoFallbackControl(FORMAT_CLASS);

    protected NoFallbackControl(List<String> formats) {
      super(formats);
    }

    public Locale getFallbackLocale(String baseName, Locale locale) {
      if (baseName == null || locale == null) {
        throw new NullPointerException();
      }
      return null;
    }
  }
}
